HSC Biology – Blueprint of Life notes – dot-point summary

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HSC Biology – Blueprint of Life notes

This is a set of HSC Biology dot-point summary notes for Blueprint of Life. HSC Biology tutoring at Dux College provides students with the right support to achieve a band 6 result in HSC Biology.

Contents

Blueprint of Life notes

Because all living things have a finite life span, the survival of each species depends on the ability of individual organisms to reproduce. The continuity of life is assured when the chemical information that defines it is passed on from one generation to the next on the chromosomes.

Modern molecular biology is providing opportunities to alter the information transferred from one generation to the next in technologies such as cloning and in the production of transgenic species.

The segregation and independent assortment of the genetic information within a species provides the variation necessary to produce some individuals with characteristic that better suit them to surviving and reproducing in their environment. Changes in the environment may act on these variations. The identification of mutations and their causes becomes important in preventing mutations and in identifying and potentially nullifying the effects of mutations in living organisms.

This module increases students’ understanding of the history, nature and practice of biology, the applications and uses of biology , the implications of biology for society and the environment and current issues, research and developments in biology.

Evidence of evolution suggests that the mechanisms of inheritance, accompanied by selection, allow change over many generations

Outline the impact on the evolution of plants and animals of: changes in physical conditions in the environment, changes in chemical conditions in the environment, competition for resources

Changes in physical conditions

  • Australia – increased temperature and decreased rainfall over the last 25 million years
    • more open woodlands and grasslands
    • the ancient kangaroo’s unspecialised teeth had to develop high crested molars to grind the tougher vegetation
    • kangaroos were previously small and omnivorous but became larger
  • England – Industrial Revolution
    • 19th century – polluted environment led to dark, sooty backgrounds for coloured moths to camouflage against
    • light coloured pepper moths were easy to see and were eaten by birds before they could reproduce
    • genes of dark-colouring were passed on to the next generation
    • as pollution was reduced, trees and backgrounds became lighter – lighter-coloured moths begin to dominate as the gene for dark-colouring is no longer favourable
    • away from industrialised cities, trees were light in colour, and lighter-coloured moths dominated

Evolution of Plants and Animals

 

Moth blueprint of life evolution

Changes in chemical conditions

  • Insecticide DDT
    • initially killed most of the mosquitoes it was sprayed upon
    • those that survived possessed a DDT resistant gene
    • this favourable gene was passed on and eventually the whole population was genetically resistant to DDT
  • Increase in soil salinity
    • plants that tolerate salinity survive e.g. saltbush
    • such plants dominate over less salt-tolerant species
  • Blowflies
    • major problem to Australian sheep industry – stresses, weakens and can be lethal when larvae burrows into wounds and wet wool
    • chemicals such as dieldrin and organic phosphates, have been used extensively
    • fly population has developed genetic resistance
    • eventually continued used of insecticide results in mutation of modifier gene that increases and maintains resistance
  • Rabbits and myxomatosis
    • in 1950, the myxoma virus was introduced to attempt to control rabbit numbers (they were a problem since 1859)
    • virus carried by fleas or mosquitoes – causes disease myxomatosis in rabbits
    • in the first few years, 99% of infected rabbits died
    • then death rate fell to 95% in 1953 and 50% in 1960
    • survivors from the first infections passed on genes of resistance
    • rabbits resistant to myxoma virus increased in number
  • Rabbits and calicivirus
    • the calicivirus (rabbit haemorrhaging disease) was introduced as a second attempt to control the rabbit population
    • spread from direct contact – death within 24 hours of infection
    • accidental release in 1995, official release in 1996
    • 90% of rabbits were killed in arid regions, 65% in wetter regions
      • significant regeneration of native vegetation in arid regions
    • September 2000 – rabbits caught with antibody that made them immune to calicivirus
    • 2002 – 40% killed in wetter areas
    • 2003 – new and cheaper method to spread disease to carrots spread around warren areas – spread to newborn rabbits

Competition for resources

  • Native species can become endangered or extinct (or restricted to some islands) due to competition with introduced species for food, access to water and nesting or burrowing sites.
    • European rabbit – bilby
    • Bitou bush – native Acacia
    • Sheep, foxes, goats, pigs, feral cats
    • prickly pear, wheat, Paterson’s curse
  • Populations may specialise on slightly different resources or breed at different times.
    • avoid direct competition
    • different species may be produced
    • fruit flies have developed different species – each confined to a different type of tree
      • different flowering and fruit times result in different breeding cycles

Describe, using specific examples, how the theory of evolution is supported by the following areas of study: palaeontology, including fossils that have been considered as transitional forms; biogeography; comparative embryology; comparative anatomy; biochemistry

Paleontology (the study of fossils)

  • Living organisms have changed over time – not just growth of individual organisms, but changes in whole species
    • Radioactive dating (radioisotopes e.g. carbon-14 being used to date fossils) shows us how old fossils are – dates for the appearance of groups of organisms
    • “Gradual” change from simple to complex life forms, indicating the development of life on earth as a “gradual” unfolding except for the Cambrian explosion
Animal Time of appearance
jawless fish 500 million years ago
bony fish 400 million years ago
amphibians 360 million years ago
reptiles 300 million years ago
birds 190 million years ago
mammals 150 million years ago

 

Plant Time of appearance
seed ferns, lycopods, horsetails, ferns 400 million years ago
gymnosperms 300 million years ago
angiosperms 185 million years ago

HSC Biology Blueprint of Life - fish to amphibians

  • Transitional forms – examples of organisms that indicate the development of one group of organisms from another or from a common ancestor – intermediate types between stages of evolution
  • Examples include:
    • fish to amphibians
      • fish that could absorb oxygen from air – 400 million years ago
      • the crossopterygian fish has bones in its fins, suggesting it could “walk” (drag itself) on land

HSC Biology Blueprint of Life - reptiles into mammals

  • Reptiles to mammals
    • mammal-like reptiles with jawbone between that of reptiles and mammals
    • evidence that these mammal-like reptiles (called therapsids) were warm-blooded
    • also monotremes lay eggs

HSC Biology Blueprint of Life - reptiles to birds

  • Reptiles to birds
    • Archaeopteryx – flying dinosaur with feathers
    • mixture of reptile and bird characteristics
    • seven known specimens
    • unknown whether feathers were for insulation or flight
    • comparatively flat sternum – today’s non-flightless birds have a keeled sternum to which the large, powerful flight muscles attach
      • scientists think the Archaeopteryx could sustain powered flight, but was probably not a very strong flier

HSC Biology Blueprint of Life plant transition

  • Plants
    • extinct seed ferns appear to be ancestors of present-day gymnosperms (conifers)
    • seed ferns look like ferns but naked seeds can be seen attached to their leaves
    • evidence suggests their life history was similar to that of gymnosperms

Biogeography (the study of the distribution of living things)

  • Charles Darwin and Alfred Russell Wallace both argued that organisms in different regions had come from ancestors in that region, and adapted over time to suit the conditions.
  • Wallace suggested Wallace’s Line which separates the distribution of organisms in Asia and Australia.
    • Australia was separated from Asia before placental mammals had evolved – marsupials in Asia were outcompeted by placental mammals
  • Barriers such as sea, rivers, mountain ranges and deserts prevent interbreeding – new species may be produced.
    • Australia’s unique flora and fauna could have been a result of evolution in isolation.
  • Ratites – cassowary and emu (Australia), ostrich (Africa), rhea (South America), kiwi (New Zealand)
    • DNA comparison suggests a common ancestor
    • Adapted to suit their own niches
  • Proteaceae family plants are found in both Australia and South Africa – land masses once joined
    • waratahs, banksias, grevilleas, telopeas

HSC Biology Blueprint of Life - Biogeography

Comparative Embryology (the study of embryos of different organisms, looking for similarities and differences)

  • All vertebrates possess pharyngeal (throat) gill pouches at some stage of development.
    • life on earth began in an aquatic environment – inherited from aquatic ancestor
  • Basic vertebrate pattern of six pairs of aortic arches is modified during later development in different vertebrates.
    • adult fish has pattern of circulation similar to basic pattern
    • frogs and humans lose several aortic arches with gills being lost and lungs developed

HSC Biology Blueprint of Life - comparative embryology

 

  • Haeckel’s embryos are a famous illustration comparing the early stages of various animals.
    • embryos appear remarkably similar
  • However, Haeckel has been widely criticised for over-exaggerating similarities between embryos.

HSC Biology Blueprint of Life - Haekels Embryos

Comparative Anatomy (the study of differences and similarities in structure between different organisms)

  • Common structures suggest common ancestry – similar genes
  • Anatomical structures with same basic plan despite different functions are homologous structures
  • Pentadactyl limb – five finger-like bones and two lower limb bones (radius and ulna)
    • Most land vertebrates possess pentadactyl limbs.
    • believed to be inherited from aquatic ancestors – the lobe-finned fish
  • Xylem – conducting vessels that transport water throughout a plant
    • Ferns, conifers and angiosperms all have vascular tissue, including xylem.

Biochemistry (the study of molecules and how they react in living things)

  • Many animals possess similar molecules – haemoglobin, RNA, hormones
  • Techniques such as assessing compatibility of blood, amino acid sequencing and DNA hybridisation help identify evolutionary relationships.
    • For example, humans are more closely related to rhesus monkeys (8 amino acid differences in haemoglobin) than to lampreys (125 amino acid differences).

HSC Biology Blueprint of Life - biochemistryExplain how Darwin/Wallace’s theory of evolution by natural selection and isolation accounts for divergent evolution and convergent evolution

The Darwin/Wallace theory details that:

  • In any population there is variation amongst the individuals
  • In nature there is a struggle for existence. Organisms with favourable characteristics survive in greater numbers and reproduce and pass on these favourable variations.
  • The next generation will have more individuals that have inherited the favourable characteristic.
  • Over time the population will change and the favourable characteristics will become more common and the population become better adapted to their environment.
  • Isolation and natural selection in the different environments may lead to enough changes to form a new species, as the two populations cannot interbreed because of geographical barriers.
    • For example: Darwin’s 14 species of finches on the Galapagos islands, each with different beaks and diets

Divergent Evolution

  • Divergent evolution is the change in a population over time so that different groups arise from a common ancestor – closely related organisms become very different
    • kangaroos – tree kangaroo (rainforest), rat kangaroo (desert), padmelon (thick scrubland) and red kangaroo (grassy plains)
    • Darwin’s finches – 14 different species of finches on the Galapagos and Cocos islands have different habitats and diets, with different body sizes and beak size and shape

HSC Biology Blueprint of Life - Darwin Wallace

 

Convergent Evolution

  • Convergent evolution involves the changes in populations that lead to similarities due to organisms in a similar environment although they are not closely related
    • sharks (fish), dolphins (mammal), seals (mammal), penguins (bird) and turtles (reptile) – streamlined bodies and fins/flippers, marine environment
    • sugar glider (Australia, marsupial) and flying squirrel (America, placental mammal) – stretched skin between fingers for gliding, arboreal habitat

HSC Biology Blueprint of Life - divergent convergent evolutionPlan, choose equipment or resources and perform a first-hand investigation to model natural selection

Coloured toothpicks represented organisms with a certain outer colour. These were scattered on grass and students attempted to pick up as many as possible in 30 seconds, representing a predator. A table revealed that orange toothpicks were chosen the most and green toothpicks were chosen the least. This demonstrated that a green outer colour would be favourable for a potential prey species in a green grassy environment as they would camouflage.

Analyse information from secondary sources to prepare a case study to show how an environmental change can lead to changes in a species

A change in environment corresponds with a change in selection pressures. This means that different characteristics will be considered favourable, and thus through natural selection, a population will evolve to suit the new environment.

For example, over the past 25 million years, Australia has become increasingly arid and there are less rainforests and more open woodlands and grasslands. The ancient kangaroo, which was small with no specialised teeth, evolved into the modern day red kangaroo, which is much larger, to help it travel quickly across open grasslands, and has high crested molar teeth for grazing. The red kangaroo also has no big toe, and longer toes than its ancestors, which assist in its speed.

The musky rat kangaroo in the rainforests of North Queensland, has a habitat similar to that of the ancient kangaroo. The musky rat kangaroo resembles the early kangaroo, with 5 toes on its hind feet, and gallops rather than hops when moving fast. It has no specialised teeth.

Perform a first-hand investigation or gather information from secondary sources (including photographs/diagrams/models) to observe, analyse and compare the structure of a range of vertebrate forelimbs

Diagrams of vertebrate forelimbs were observed, with colour coding for different bones. Similarities were noted with most vertebrates having humerus, ulna, radius, carpals, metacarpals and phalanges. Differences were also noted:

  • Humans have opposable thumbs for manual dexterity.
  • Cats have metacarpals and phalanges compacted together for walking on forelimbs.
  • Whales have short and thick bones to form a paddle which is strong and flat (water has high viscosity).

HSC Biology Blueprint of Life - vertebrate forelimbsUse available evidence to analyse, using a named example, how advances in technology have changed scientific thinking about evolutionary relationships

DNA Hybridisation

  • Heat unwinds and separates the strands that make up the double helix.
  • Segments of DNA from two different species are cooled together.
  • On cooling, hydrogen bonds reform between complementary base pairs.
  • The degree of bonding reflects the degree of genetic similarity between species.
  • The degree of bonding is determined by the temperature necessary to separate the mixed strands again.

DNA hybridisation allows scientists to determine the genetic similarity between species, and thus map out their evolutionary pathways more accurately. DNA hybridisation on primates shows that humans are more closely related to chimpanzees than to gorilla.

Amino Acid Sequencing

  • Proteins are synthesised according to a DNA code.
  • Therefore a polypeptide sequence reflects the DNA code, and similarities in amino acid sequence imply that organisms are closely related.
  • Amino acid sequencing can be determined using technology that cleaves the chain at certain places and logically determining the amino acid sequences e.g. Edman degradation.

Studies on haemoglobin show that one out of the four polypeptides (containing 146 amino acids) is identical for humans and chimpanzees. The same chain in gorillas has only 45 amino acids the same.

Immunisation

  • Human serum (blood minus blood cells and clotting agents) is injected into another mammal, such as a rabbit.
  • The rabbit’s immune system produced antibodies to these human proteins.
  • The serum from the rabbit (containing antibodies for human proteins) can be used in tests with the serum of other mammals.
  • The amount of precipitation that occurs is a measure of the difference in some of their proteins, and thus an indirect measure of relationships between mammals.
  • More precipitation corresponds with a closer relationship – precipitation produced by reaction with human serum is taken as 100%.

Studies with immunisation show that between humans and chimpanzees, there is 97% precipitation.

HSC Biology Blueprint of Life - evolutionary relationships

Analyse information from secondary sources on the historical development of theories of evolution and use available evidence to assess social and political influences on these developments

Beginning of 19th Century Much evidence was available for evolution but no plausible mechanism. People were much more comfortable believing that species were created independently.
1801 Jean-Baptiste Lamarck suggested that changes in environment causes changes in an organism based on the use and disuse of a certain organ or structure. These acquired characteristics were proposed to be heritable. His theory of the inheritance of acquired characteristics was a possible mechanism for evolution.
1831 – 1836 Charles Darwin served as naturalist aboard the Beagle. He visited the Galapagos islands in 1835 and Australia in 1836, where he observed the flora and fauna and noted Australia’s geographical isolation.
1836 – 1858 Darwin developed his theory of natural selection.
1848 – 1852 Alfred Russell Wallace visited South America and observed species there.
1854 – 1862 Wallace visited Malaysia and observed species there.
1858 Wallace wrote a letter to Darwin detailing his very similar theory or natural selection, prompting Darwin to present his ideas. Papers by Wallace and Darwin were jointly presented.
1859 Charles Darwin published On the Origin of Species. He was vehemently attacked by the church for suggesting that humans had simply evolved from more primitive animals and were not “made in God’s image”. Cartoons were published in the media of Darwin’s head on the body of an ape, mocking his theory of evolution.
20th Century Neo-Darwinism developed, where concepts of Mendelian and non-Mendelian genetics are used to explain the theory of evolution by natural selection.

Gregor Mendel’s experiments helped advance our knowledge of the inheritance of characteristics

Outline the experiments carried out by Gregor Mendel

HSC Biology Blueprint of Life - Gregor Mendel

  • Gregor Mendel (1822-1884), an Augustinian monk at Brunn in Moravia (today Brno in the Czech Republic), used the garden pea (Pisum sativum) to study inheritance.
  • He is known as the father of genetics.
  • In 1866 he published results of his work in a paper called “Experiments in plant hybridisation”, but it was ignored. Not until the early 20th Century was Mendel’s work acknowledge and appreciated.
  • He worked with pure breeding plants and then hybrids, studying the inheritance of one particular trait at a time, including:
    • seed form
    • flower colour
    • seed colour
    • stem length
    • pod form
    • pod colour
  • Each trait existed as two alternate forms.
  • When pure breeding plants with different forms of a trait were crossed, one of the alternate forms of the trait was lost in the F1 generation but reappeared in the offspring when two F1 plants were crossed.
  • Mendel called the factor expressed in the F1 generation the “dominant trait” and the other alternate form the “recessive trait”.
  • He was able to predict ratios of various types of offspring from two parents using mathematical calculations.
  • He concluded that factors responsible for the inheritance of characteristics occur as discrete units and that they were inherited in pairs, with one factor from each parent.
    • Law of Segregation – During reproduction the two factors that control a certain characteristics segregate, one appearing in each gamete. These factors match at fertilisation.
    • Law of Independent Assortment – Each pair of factors sorts out independently of all the other pairs at gamete formation.
      • Mendel also experimented with two traits at a time to find out if they were inherited independently. (We now know that the genes coding for traits he examined were on different chromosomes.)

Describe the aspects of the experimental technique used by Mendel that led to his success

Accuracy Reliability Validity
Quantitative data – Mendel counted and meticulously recorded exact numbers of plants with each characteristic. Repetition – Mendel performed many repetitions of each genetic cross. Controlled experiment – Mendel studied only one characteristic at a time, although he studied a large number of characteristics in total (changing one variable at a time).
Careful records – Mendel meticulously recorded his data. Large sample sizes – Mendel used thousands of plants for each genetic cross to be trialled. Pure-breeding plants – Mendel did this by ensuring self-pollination (bags over plants) for many generations over a period of two years.
Avoidance of accidental cross-pollination or self-pollination – To ensure cross-pollination, Mendel removed stamens of flowers and then brushed pollen from another plant onto the stigma with a paintbrush or forceps.
Use of garden peas – Garden peas produced new generations quickly and had easily distinguishable characteristics.
Mathematical analysis Mendel applied mathematical formulae and statistics to arrive at his conclusions

Describe outcomes of monohybrid crosses involving simple dominance using Mendel’s explanations

Two different parents – F1 generation only has the dominant trait

F1 crossed – F2 generation has dominant trait: recessive trait = 3:1

Distinguish between homozygous and heterozygous genotypes in monohybrid crosses

Genotype = alleles present that control a characteristic e.g. Tt

Phenotype = outward appearance of the organism e.g. tall

When both alleles are the same for a particular characteristic e.g. TT or tt, the organism is homozygous for that trait.

If the alleles are different e.g. Tt, the organism is heterozygous for that trait.

Distinguish between the terms allele and gene, using examples

A gene is a section of DNA coding for a polypeptide that may express itself in the phenotype for that trait. An allele is an alternative form of a gene. For example, there are two alleles for height in pea plants, one for tall pea plants and one for short pea plants.

Explain the relationship between dominant and recessive alleles and phenotypes using examples

When both alleles are present, a dominant allele masks the effect of the recessive allele. For example, in a pea plant heterozygous for plant height, the phenotype is tall (dominant phenotype) because the allele for tallness is dominant over the allele for dwarfishness. But in homozygous plants, the plant can be tall (genotype TT, dominant phenotype) or short (genotype tt, recessive phenotype).

Outline the reasons why the importance of Mendel’s work was not recognised until some time after it was published

At the time:

  • Lack of recognition – Mendel was not recognised as a high profile member of the scientific community, having done no prior significant research and having no interaction with other well-known scientists. He presented his papers to a very small group of scientists (about 40) at two meetings in 1865 of The Natural Science Society of Britain – a fairly low profile gathering in the province of Moravia.
  • Lack of understanding – Most scientists did not understand his paper. Very little was known about cells; chromosomes, mitosis and meiosis were unknown and the studies of genetics did not exist.
  • Originality – Mendel’s work differed radically from previous research – scientists did not recognise its significance, as the belief of ‘blending’ was widely accepted. Mendel’s use of mathematics and statistics was different to the norm in biology at that time.
  • Diversion of attention – Both Darwin and Wallace were working on their theories of evolution at the time and much scientific interest was focussed on their research. Darwin published On the Origin of Species in 1859.

Later (1900):

  • Further experiments by three different cytologists working independently were performed, producing similar data.
  • Mendel’s work has been widely acknowledge and valued since then.

Perform an investigation to construct pedigrees or family trees, trace the inheritance of selected characteristics and discuss their current use

Pedigrees are useful for assessing a person’s likelihood for developing a genetic disease, for assessing an animal’s value for breeding and for determining the inheritance pattern for a characteristic.

In general, squares denote males and circles denote females. A coloured-in shaped represents an individual showing the characteristic.

  1. Solve problems involving monohybrid crosses using Punnett squares or other appropriate techniques.

Homozygous dominant/Homozygous recessive

  T T
t Tt Tt
t Tt Tt

All individuals have genotype Tt and show the dominant trait.

Homozygous dominant/ Heterozygous

  T T
T TT TT
t Tt Tt

Genotypic ratio of TT:Tt = 1:1

All individuals show the dominant trait.

Homozygous recessive/ Heterozygous

  t t
T Tt Tt
t tt tt

Genotypic ratio of Tt:tt = 1:1

Phenotypic ratio of dominant trait: recessive trait = 1:1

Heterozygous/ Heterozygous

  T t
T TT Tt
t Tt tt

Genotypic ratio of TT:Tt:tt = 1:2:1

Phenotypic ratio of dominant trait: recessive trait = 3:1

Process information from secondary sources to describe an example of hybridisation within a species and explain the purpose of this hybridisation

Hybridisation is when two genetically different strains are crossed to produce an offspring with more desirable characteristics than either parent.

  • Labradoodle – cross between Labrador and poodle (within the species of dog)
    • does not shed hair – important for people with asthma or allergies
    • no body odour
    • do not need constant bathing and brushing
    • easy to train
    • can be trained as guide dogs
  • William Farrer bred Yandilla Wheat from Indian Wheat and Canadian Fife Wheat
    • drought tolerance
    • resistance to sun
    • resistance to disease
    • good milling and baking qualities
    • late maturing

Chromosomal structure provides the key to inheritance.

Outline the roles of Sutton and Boveri in identifying the importance of chromosomes

Walter Sutton (1877-1916) studied meiosis in cells of grasshoppers (Brachystola magna). Sutton’s observations revealed that:

HSC Biology Blueprint of Life - Walter Sutton

  • Chromosomes occur in distinct pairs as distinct entities, visible during meiosis in grasshopper cells.
    • One chromosome of each pair is paternal and the other maternal (today termed homologous pairs).
    • These chromosomes in each pair have the same size and shape.
  • During meiosis, the chromosome number of a cell is halved.
    • The chromosomes in each pair separate.
    • Each gamete receives one chromosome from each pair.
  • Fertilisation restores the full number of chromosomes in the zygote.

HSC Biology Blueprint of Life - Mendelian factors

Sutton concluded that:

  • Chromosomes arrange themselves independently along the middle of the cell just before it divides.
  • Chromosomes are units involved in inheritance. Sutton believed several “Mendelian factors” must be present in one chromosome.
  • If two characteristics are on the same chromosome (linked genes) they will move together rather than separately according to Mendel’s law of independent assortment.

Theodor Boveri carried out experiments on sea urchin eggs between 1896 and 1904. He studied the behaviour of the cell nucleus and chromosomes during meiosis and after fertilisation.

HSC Biology Blueprint of Life - Theodore Boveri

Sea urchin eggs could be easily fertilised in a laboratory and have a quick (48 hour) time frame for larval development.

HSC Biology Blueprint of Life - Sea Urchins

Boveri’s experiments showed that:

  • The nucleus of the egg and sperm each contribute the same amount of chromosomes to the zygote, thus connecting chromosomes and heredity.
  • When a normal egg and sperm fused, the resulting offspring showed characteristics of both parents.
  • If the nucleus of only one parent was present, the larvae resembled that parent, but showed abnormalities.
    • When an egg with its nucleus removed was fertilised with a sperm, the resulting sea urchin larvae showed characteristics similar the male parent. However, they were smaller, had only half the normal number of chromosomes and showed some abnormalities.

Boveri deduced that:

  • A complete set of chromosomes (in pairs) is required for normal development.
  • The inheritance “factors” are found on chromosomes within the nucleus – chromosomes are the carriers of heredity.
  • There are more hereditary “factors” than chromosomes and so there must be many factors (today known as genes) on one chromosome.

Together in their independent studies, Sutton and Boveri are considered the founders of the chromosome theory of inheritance (the Sutton-Boveri theory). They deduced that chromosomes are hereditary units and occur in pairs.

  Before Sutton and Boveri’s work After Sutton and Boveri’s work
Where in the cell are heredity factors found? Cytoplasm and nucleus Nucleus only
What material stores the heredity information? Unsure – perhaps proteins? A full set of paired chromosomes, where many heredity factors are carried on each chromosome
How are inherited factors passed to the next generation? Gametes transport “factors”, but how or what these factors were was unknown Random assortment during meiosis – units of inheritance carried on chromosomes in gametes
Nature of chromosomes Chromosomes were believed to disappear and reappear and were all believed to the same size and shape Chromosomes occur in set numbers in every cell in pairs and each pair of chromosomes has the same size and shape

Describe the chemical nature of chromosomes and genes

Chromosomes consist of 40% DNA (deoxyribonucleic acid) and 60% protein (histone). The protein supports and protects the chromosome, as the DNA is wound around the protein.

Each gene is made up of a portion of DNA that stores information as a coded sequence, and each coded sequence is located at a particular site, or locus.

Identify that DNA is a double-stranded molecule twisted into a helix with each strand comprised of a sugar-phosphate backbone and attached bases – adenine (A), thymine (T), cytosine (C) and guanine (G) – connected to a complementary strand by pairing the bases, A-T and G-C

In 1953, Watson and Crick described the DNA molecule as a double helix.

  • The double strands are made up of alternating deoxyribose sugar and phosphate units.
  • Each sugar is attached to a nitrogenous base.
  • The subunits of DNA are called nucleotides, each consisting of a phosphate group, sugar and nitrogenous base.
  • There are four types of nitrogenous bases: adenine, cyanine, guanine and thymine.
  • A only bonds to T, and C only to G.
  • These bases make up the genetic code.

HSC Biology Blueprint of Life - Watson Crick

 

HSC Biology Blueprint of Life - Watson Crick DNA bases

Explain the relationship between the structure and behaviour of chromosomes during meiosis and the inheritance of genes

Inheritance of genes Structure and behaviour of chromosomes
Factors (genes) responsible for heredity occur in pairs. Chromosomes occur in pairs in body cells.
During meiosis one of each of these factors passes into the gametes. Alleles for a particular characteristic are located on each member of a homologous pair, which segregate during meiosis.
Only one of each pair of genes is present in each gamete; the number of genes in gametes is half that of body cells. Only one allele is present for what used to be a pair. The number of chromosomes going into each sperm and ovum at the end of meiosis is half the number found in somatic cells.
Four haploid cells are formed in meiosis. Meiosis involves two divisions, hence forming four daughter cells. They are haploid because chromatids separate in the second stage.
Genes may change position during meiosis, leading to increased variation: recombinant types can be produced. Crossing over may occur when two chromosomes swap chromatid parts.

Explain the role of gamete formation and sexual reproduction in variability of offspring

Genetic variation is increased by:

  • Random segregation of homologous pairs in meiosis. Most organisms have many chromosomes so there are many possible combinations.
  • Crossing over can occur during meiosis between homologous pairs of chromosomes. Portions of chromatids are exchanged, doubling the number of different types of gametes.
  • Gametes join randomly in fertilisation with many possible combinations. Each individual is a unique combination of traits from each parent.

Another source of genetic variation, with little to do with gamete formation and sexual reproduction, is mutation. Mutations can apply to both sexually and asexually reproducing organisms.

  1. Describe the inheritance of sex-linked genes, and alleles that exhibit co-dominance and explain why these do not produce simple Mendelian ratios.

Sex linkage

  • Males receive a single X-chromosome from the mother and a Y-chromosome from the father.
  • Females receive an X-chromosome from the father and one from the mother.
  • Often a gene is located on an X-chromosome.
  • Because X-linked characteristics are often recessive, and females have two X-chromosomes, so that they can be heterozygous and do not exhibit the trait, X-linked traits are more common in males than in females (in humans).
  • Mendelian ratios do not occur as the two alleles for each characteristic are not necessarily both existent (males only have one X-chromosome).

Codominance

  • Both alleles can be expressed in the heterozygous form.
  • There are 3 possible phenotypes.
  • Mendelian ratios do not account for the third phenotype.
  1. Describe the work of Morgan that led to the understanding of sex linkage.
  • In the early 1900s, Thomas Hunt Morgan tried to replicate Mendel’s work using the fruit fly Drosophila melanogaster.
    • These flies are small and can be kept in small glass containers, breed easily in captivity and the two sexes are easily distinguishable.
  • Morgan crossed a white-eyed male with normal, pure-breeding red-eyed females and all the offspring had red eyes.
    • He concluded that red was dominant over white eye colour.
  • When he crossed two of the red-eyed offspring, the next generation was red: white in the ratio 3:1 (as Mendel would have predicted), but all the white-eyed offspring were male.
    • By pure-breeding, Morgan bred white-eyed females with pure-breeding red eyed males, and found equal numbers of red-eyed female and white-eyed males.
  • Morgan hypothesised that the eye colour gene is carried on the X-chromosome.
    • Further tests showed Morgan’s hypothesis to be correct.
  • Morgan was awarded a Nobel Prize in 1933.
  1. Explain the relationship between homozygous and heterozygous genotypes and the resulting phenotypes in examples of co-dominance.

Both alleles are expressed in the heterozygous genotype. The phenotype is different to both homozygous forms. For example, roan cattle are different to both red and white cattle.

  1. Outline the ways in which the environment may affect the expression of a gene in an individual.

Environment may affect gene expression, so that genes may or may not be fully expressed. Factors include:

  • Nutrition – identical twins may have different birth weights due to different positions in the uterus and therefore a difference in nutrition
  • Temperature – Himalayan rabbits are black when raised at 5°C, white with black extremities when raised at 25°C and completely white when raised at 35°C
  • pH – hydrangeas have pink flowers in alkaline soils and blue flowers in acidic soils (pH<6)
  • Oxygen availability – humans at high altitudes have higher red blood cell counts
  • Light – Arctic foxes have dark coats in summer and light coats in winter

Process information from secondary sources to construct a model that demonstrates meiosis and the processes of crossing over, segregation of chromosomes and the production of haploid gametes

Pipecleaners represented chromatids. Different colours for maternal and paternal chromosomes were used. Little bits of pipecleaner were used for crossing over.

Advantages

  • Colour-coding
  • Shows different gametes and crossing over
  • Easy to obtain pipe cleaners

Limitations

  • No mechanism – spindle fibres
  • No sense of the time taken in each phase
  • Only practical to use a diploid number of four. In reality, many organisms have many more chromosomes.

Solve problems involving co-dominance and sex-linkage

Roan cattle cross roan cattle

  R W
R RR RW
W RW WW

Genotypic ratio of RR:RW:WW = 1:2:1

Phenotypic ratio of red:roan:white = 1:2:1

Haemophilic male and carrier female

  Xh Y
XH XHXh XHY
Xh XhXh XhY

Genotypic ratio is XHXh:XHY:XhXh:XhY

Phenotypic ratio is normal (carrier) female: normal male: haemophilic female: haemophilic male

Identify data sources and perform a first-hand investigation to demonstrate the effect of environment on phenotype

Radishes were grown in two petri dishes. One was kept in the light and one was kept in the dark.

The radishes in the dark grew taller faster but had yellow leaves. The ones in the light reached a shorter height in the same time compared to the radishes in the dark. However, when the radishes in the dark were moved into the light, their leaves became green, indicating that the gene was undamaged, just not expressed whilst in the dark.

The structure of DNA can be changed and such changes may be reflected in the phenotype of the affected organism

Describe the process of DNA replication and explain its significance

DNA replication involves copying a strand of DNA. This process occurs during mitosis and meiosis.

  • An enzyme causes the DNA helix to unwind from around the protein histone.
  • The DNA unzips to form two single strands – hydrogen bonds between bases are broken.
  • Nucleotides are added to each single strand, with complementary bases added to each original base (the original strand codes for the other strand).
    • catalysed by DNA polymerase

DNA replication allows the process of mitosis and meiosis to occur, which allow a species to survive and continue. Large amounts of coded information can pass from one generation to the next.

Mutations in the code result in genetic variation, which may be favourable for evolution.

Outline, using a simple model, the process by which DNA controls the production of polypeptides

Nucleus

  • DNA in the area of the gene unwinds and unzips
  • transcription – a single-stranded messenger-RNA molecule is created based on complementary bases with the DNA template strand
    • RNA polymerase is an enzyme that catalyses transcription.
  • mRNA is modified so that it consist only of the base sequence that will code for the polypeptide (introns cut out, exons kept in).
  • mRNA moves out into the cytoplasm.

Cytoplasm

  • mRNA attaches to a ribosome.
  • translation – transfer-RNA molecules bring in corresponding amino acids and attach to the mRNA according to their complementary bases.
    • amino acids join with peptide bonds
    • after the next tRNA comes in, the first one leaves to be reloaded
    • anticodons on tRNA correspond with codons on mRNA
  • A polypeptide is formed

HSC Biology Blueprint of Life - Polypeptide Formation

 

Explain the relationship between proteins and polypeptides

A polypeptide is a chain of many amino acids held together by peptide bonds. A protein can be formed from one polypeptide or several polypeptides linked together and then folded into a 3D shape. For example, haemoglobin is made up of four polypeptide chains.

Explain how mutations in DNA may lead to the generation of new alleles

A mutation is a change in the genetic code. A gene is a specific section of DNA that codes for a polypeptide and this may control a certain trait. A change in the DNA code may alter the polypeptide produced, creating a new allele.

If this occurs in the sex cells of an organism, the mutation can be inherited.

There are different types of mutations:

  • gene mutations (one gene) and chromosome mutations (whole blocks of genes)
  • harmful, beneficial or neutral (beneficial mutations could lead to a new species through natural selection)
  • somatic (body cells) or gametic (sex cells)
  • spontaneous (error in natural process of DNA replication) or induced (environmental agent)

Discuss evidence for the mutagenic nature of radiation

A mutagen is a natural or human-made agent (physical or chemical) which can alter the structure or sequence of DNA. They may be carcinogens (causing cancer) or teratogens (causing birth defects).

Ultraviolet radiation

  • known mutagen
  • can cause bases in DNA to be lost (deletion)
  • can cause thymine bases in the same strand to link together – replication cannot occur and the cell will die
  • Humans exposed to high doses of ultraviolet radiation show an increased incidence of skin cancer.
    • The ozone ‘hole’ over Antarctica, caused by CFCs, CO, SO2 and oxides of nitrogen, has led to more intense doses of UV radiation than before.

Ionising radiation

  • alpha and beta radiation
  • can break DNA strands or even whole chromosomes if at a high enough energy levels
    • leads to mutation or cell death
  • X-rays were first considered a novelty but are now known to be a mutagen
    • Before, it was possible to purchase an “X-ray machine” for home entertainment.
    • In the 1950s and 1960s, people had their feet X-rayed when buying shoes.
    • Today, X-rays are only used with great care by doctors, dentist and scientists.
    • Hans Muller received the Nobel Prize in 1927 for showing that genes could mutate when exposed to X-rays.
    • Beadle and Tatum used X-rays to produce mutations in bread mould.
  • Many scientists who worked with radiation died of cancer, including Marie Curie and her daughter, who both died of leukaemia.
  • Survivors of the atomic bombs on Hiroshima and Nagasaki in 1945 showed a tenfold increase in cancer deaths (especially leukaemia) directly after the bombs were dropped.
    • Both survivors and their descendants show immediate damage of the DNA of their cells (mutations in the sex cells).
  • Nuclear accidents in Chernobyl (1986) and Fukushima (2011) show evidence of increased birth defects and cancer in the region (Ukraine or Japan).
    • Chernobyl also involved a great environmental catastrophe as the radiation with a long half-life spread into food, soil, land and waterways.
    • Two in every three calves born in the first five years were stillborn.
    • As of 2004, it was estimated that half a million people would die prematurely from radiation-induced cancers.

Explain how an understanding of the source of variation in organisms has provided support for Darwin’s theory of evolution by natural selection

The sources of variation include:

  • Random segregation of homologous pairs of chromosomes in meiosis
  • Crossing over in meiosis
  • Random pairing of gametes in sexual reproduction
  • Mutations

Darwin’s theory of natural selection states that there is variation within a species. Organisms with more favourable characteristics for a particular environment are more likely to survive and reproduce, passing on these favourable variations.

Describe the concept of punctuated equilibrium in evolution and how it differs from the gradual process proposed by Darwin

Darwin’s theory of evolution by natural selection proposes that populations evolved slowly and gradually over time. This means the fossil record should reflect small changes in each generation over a long period of time. There are few instances of this evidence. For example, the lineage of the horse over 40 million years has been mapped as transitional forms have been found.

In most species, their appearance and extinction are sudden, as the environment is stable for some time, then changes rapidly. In 1972, Niles Eldridge and Stephen Jay Gould proposed the theory of punctuated equilibrium. This suggests that evolution is a sudden process rather than slow, gradual changes. Long periods of little change are punctuated by shorter periods of rapid change. Examples include:

  • Globorotalia – a marine microfossil. A second species suddenly appeared in the Indian and Atlantic Oceans but a transitional form has been found in the South Pacific Ocean. The two forms coexist today.
  • A trilobite genus Phacops – A new species suddenly appeared in the fossil record, but transitional forms have been found in one location in New Hampshire, USA.
  • Dinosaurs such as Tyrannosaurus and Stegoceras – These were unchanged for 5 million years in the Judith River Formation in Montana, USA, but new species ‘suddenly’ appeared 500 000 years later. Further research revealed that in those 500 000 years, sea levels rose and drowned the Judith River Formation, and dinosaurs would have moved out and changed in a different environment. In other areas of Montana transitional forms have been found. The changed dinosaurs (Daspletosaurus instead of Tyrannosaurus and Pachycephalosaurus instead of Stegoceras) returned when sea levels dropped.

Perform a first-hand investigation or process information from secondary sources to develop a simple model for polypeptide synthesis

  • Ribbon – sugar
  • Straw – phosphate group
  • Different coloured pegs – different bases
  • Pegging pegs together – hydrogen bonds
  • Threading objects onto ribbon – covalent bonds
  • Large paper – ribosome
  • Small paper of different colours – amino acids
  • Peptide bonds – sticky tape
Advantages Limitations
Colour-coding the pegs accounts for different bases. It is easy to visually note complementary bases, and the presence of thymine in DNA and uracil in RNA. The model implies that phosphate groups and nitrogenous bases are ‘threaded’ onto the sugar, which is not true. Nucleotides are individual units.
Colour-coding the paper accounts for different amino acids. No enzyme activity was modelled – RNA polymerase was not present in the model.
Colour-coding the ribbon accounts for deoxyribose sugar in DNA and ribose sugar in RNA. There was no mechanism to show that the mRNA was transcribed in the nucleus and then moved into the cytoplasm.
The pegs joined together were easy to undo, hence modelling the weak nature of hydrogen bonds. Similar, unthreading the objects was rather time- and energy-consuming, modelling the strong nature of covalent bonds. There was no chemical structure shown. It was implied that hydrogen bonds involved physical contact and overlapping of bases, which is not true.
  The peptide bonds did not account for the elimination of water or enzyme activity.
  The model implies that polypeptide chains are short, and does not show start or stop codons. It would be impractical to model a polypeptide of realistic length (short ones have 50 amino acids).

Analyse information from secondary sources to outline the evidence that led to Beadle and Tatum’s ‘one gene – one protein’ hypothesis and to explain why this was altered to the ‘one gene – one polypeptide’ hypothesis

George Beadle and Edward Tatum hypothesised that one gene controls the production of one enzyme. They worked on the bread mould Neurospora crassa. Using X-rays, they produced a mould that was unable to produce a specific amino acid, because it lacked a necessary enzyme.

  • Growth of different strains with different combinations of nutrients helped establish which enzyme was lacking in each mutant strain.
  • Normal mould grew even on minimal medium, but mutant mould required additional nutrients.
  • An analysis of each mutant strain showed a difference in one gene which caused a block at one step in the metabolic pathway.

Beadle and Tatum won the Nobel Prize for Physiology of Medicine for their work in 1958.

The one gene-one enzyme hypothesis was later altered to the one gene-one protein hypothesis because not all proteins are enzymes. This later became the one protein-one polypeptide hypothesis because not all proteins are made up of one polypeptide.

HSC Biology Blueprint of Life - one gene one protein

 

HSC Biology Blueprint of Life - one gene one protein

Process information to construct a flow chart that shows that changes in DNA sequences can result in changes in cell activity

Changes in DNA sequence will alter the codons on the mRNA, which may change the amino acid sequence as different tRNA molecules will bring different amino acids. The omission or addition of one nitrogenous base will cause a shift in the entire DNA molecule, causing a different polypeptide to be produced.

For example, if thymine were omitted:

HSC Biology Blueprint of Life - thymine omitted

A different polypeptide will fold different to form a different protein or enzyme. As enzymes control cell activity, modifying the DNA, which changes the enzyme, will cause changes in cell activity.

Process and analyse information from secondary sources to explain a modern example of ‘natural’ selection

  • The use of antibiotics is a selection pressure.
  • Bacteria resistant to antibiotics survive and reproduce quickly.
  • For example, Staphylococcus aureus (golden staph) have developed to be resistant to most modern antibiotics, due to overuse of antibiotics. (MRSA – methicillin resistant staphylococcus aureus)
  • This means that resistant bacteria are entering our food.
  • Over many generations (for bacteria this is very quick), the favourable characteristic of resistance will be more common and the population will be changed by natural selection.
  • DDT was an insecticide widely used to control household flies (which developed resistance) and the Anopheles mosquito which carried malaria. The widespread use of DDT in agriculture led to a rapid increase in resistance to it among Anopheles mosquitoes and a resurgence in malaria resulted. Moreover, the malaria protozoan itself was becoming resistant to the anti-malarial drugs that were being used.
  • DDT was in fact banned around this time because of environmental issues; being fat soluble and virtually non-biodegradable, DDT tended to accumulate in organisms – eggshells of Alaskan falcons became thinner as result of DDT poisoning.

Process information from secondary sources to describe and analyse the relative importance of the work of: James Watson, Francis Crick, Rosalind Franklin, Maurice Wilkins, in determining the structure of DNA and the impact of the quality of collaboration and communication on their scientific research

Scientist Work and contribution Collaboration and Communication
James Watson
  • In 1953, cracked the DNA code with Crick
  • Awarded Nobel Prize in 1962
  • Later he increased understanding of the genetic code and how DNA triplet code identifies amino acids and thus controls protein synthesis
  • Worked closely with Francis Crick
  • Bounced ideas off everywhere, including Wilkins who showed them the photograph taken by Franklin
Francis Crick
  • In 1953, cracked the DNA code with Watson
  • Awarded Nobel Prize in 1962
  • Later continued to study DNA and the way genetic information was coded
  • Worked closely with James Watson
  • Bounced ideas off everywhere, including Wilkins who showed them the photograph taken by Franklin
Maurice Wilkins
  • Successfully extracted some fibres from a gel of DNA in early 1950s
  • Franklin photographed them and Wilkins showed the photo to Watson and Crick
  • Awarded Nobel Prize in 1962
  • Got along with Watson and Crick
  • Showed them the X-ray crystallography photograph without Franklin’s knowledge or permission
Rosalind Franklin
  • Used X-ray crystallography to map the locations of atoms in the DNA molecule
  • First to state that the phosphates lie on the outside
  • Described basic double helical structure
  • Died of cancer in 1958 aged 37
  • Her work was shown to Watson and Crick

 

  • Rosalind Franklin and Maurice Wilkins were X-ray crystallographers at King’s College in London.
    • They were peers, but Wilkins misunderstood their relationship from the start, thinking of Franklin as an assistant.
    • There were few women in science at the time.
    • Franklin’s work on X-ray diffraction showed that DNA had the characteristics of a helix.
  • James Watson and Francis Crick worked at Cambridge University.
    • Wilkin’s showed them a photo taken by Franklin, which was enough for them to develop their model of the double helix.
    • Watson and Crick also bounced ideas of many other scientists, including those working on the nitrogenous bases.
    • In particular, Edwin Chargraff in the 1940s realised that the amount of guanine is the same as the amount of cytosine and the amount of adenine is the same as the amount of thymine, suggested the A-T and C-G pairing.
  • Rosalind Franklin died of cancer in 1958, aged 37.
  • Watson, Crick and Wilkins received the Nobel Prize for their work in 1962. Unfortunately, the Nobel Prize cannot be awarded posthumously.

Current reproductive technologies and genetic engineering have the potential to alter the path of evolution

Identify how the following current reproductive techniques may alter the genetic composition of a population: artificial insemination, artificial pollination, cloning

Artificial Insemination

  • Semen containing sperm is injected into the female’s reproductive tract.
  • AI is important in modern animal husbandry.
    • used to produce offspring with favourable characteristics e.g. disease-resistant cattle
    • semen can be transported over large distances and used to inseminate many females
    • frozen semen can be stored
    • also increases breeding life of a male – dead males can be used
  • But consistent sperm donors reduce genetic diversity of the population.
    • In a changing environment, the lack of diversity could endanger the survival of the species.
  • AI is also important in zoos for endangered species.

Artificial Pollination

  • Pollen of anthers is transferred onto the stigma of another plant.
  • AP is important in horticulture, to produce offspring with favourable characteristics e.g. plant hybrids for flower colour or disease resistant fruit.
  • AP can increase genetic diversity by creating new varieties but overuse may lead to entire areas of crops being susceptible to a specific pest if all plants are too similar.
    • Irish Potato famine (1845-1851) – fungal disease, one million people died due to the crop failure

Cloning<

  • process which produces genetically identical organisms through non-sexual means
    • plant cloning e.g. cuttings, tissue culture, bulbs
  • Animal cloning of mammals is more recent and not yet used in large scale commercial agriculture.
  • Continued use of a limited genetic pool in plants can cause problems if environmental conditions change e.g. potato famine in Ireland.
  • All clones are genetically identical.
  • cloning has produced seedless watermelons – decreased genetic diversity
  • cloning of animals could solve many medical issues – e.g. Polly could produce missing clotting factor in haemophiliacs – pharming
  • Dolly was cloned by Somatic Cell Nuclear Transfer
    • An enucleated egg cell has the nucleus of a somatic cell inserted.

HSC Biology Blueprint of Life - Dolly

 

Outline the processes used to produce transgenic species and include examples of this process and reasons for its use

Methods for inserting a gene

  • microinjecting into an animal egg using a fine tube e.g. salmon
  • using harmless viruses to carry genes into a host
  • inserting DNA into plant cells on gold or tungsten particles (biolistics, gene gun)
  • using Agrobacterium, a bacterium that naturally transfers DNA into plants e.g. BT cotton (Bacillus Thuringiensis)

Animal: Salmon

  • Gene coding for protein, bGH (bovine growth hormone) has been inserted into salmon by microinjecting it into an animal egg using a fine tube.
  • Fish reach maximum size faster.
  • Fish farming reduces depletion of natural populations.
  • Fish kept in ponds – could upset or destroy natural ecosystems if they escape into the wild
  • religious and cultural debate
  • transfer of allergens
  • consumer concerns
  • patents: monopoly

Plant: BT Cotton

  1. A normal cotton seedling is cut into small pieces and grown into embryo.
  2. BT gene from bacteria is extracted using restriction enzymes.
  3. Agrobacterium tumefaciens acts as vector to insert genes.
  4. Cotton plant embryos are dipped in a solution of recombinant Agrobacterium.
  5. Embryos grown in tissue culture.
  • Some resistance has developed – now Bollgard cotton has two inserted genes compared to Ingard
  • if grown at expense of other varieties –> reduced variation
  • could escape to form uncontrollable weeds

HSC Biology Blueprint of Life - BT Cotton

 

HSC Biology Blueprint of Life - Gene Insertion

Discuss the potential impact of the use of reproduction technologies on the genetic diversity of species using a named plant and animal example that have been genetically altered

Reproductive technologies include artificial insemination, artificial pollination, cloning and the production of transgenic species.

Transgenic salmon with bovine growth hormone inserted

  • Fish farming reduces the depletion of natural populations due to fishing.
  • However, if GM fish escape into the wild, they may upset or destroy natural ecosystems as they reach their maximum size faster than natural salmon.

Nevertheless, GM salmon are kept in ponds and there is very little risk that they may escape into natural ecosystems.

BT cotton with gene from Bacillus thuringiensis bacterium

  • The disease resistance of BT cotton allows farmers to use less pesticide, thus having less of an impact on natural ecosystems. Useful insects are not harmed and fewer chemicals are introduced into the environment.
  • If BT cotton escapes into natural ecosystems and interbreeds with weeds, “super-weeds” that are resistant to insects may be produced, upsetting the natural balance of the ecosystem.
  • If cotton plants are cloned before embryos are dipped into the solution of Agrobacterium, diversity is reduced and the cotton plant could face extinction if there is a sudden environmental change.

Because of their great yield and reduction of pesticide use, along with the low risk of escape into the wild, BT cotton is widely used and is considered safe. Seed banks are kept by most countries to ensure that genetic information of many varieties of cotton is not lost.

Process information from secondary sources to describe a methodology used in cloning

Somatic Cell Nuclear Transfer

  1. The nucleus is removed from an unfertilised egg cell.
  2. The nucleus of a body cell is injected into the enucleated egg cell.
  3. The cell is cultured then implanted into a surrogate mother.
  4. When it is born, the organism is a clone to the sheep that donated the somatic cell.

HSC Biology Blueprint of Life - Somantic Cell Nuclear Transfer

Analyse information from secondary sources to identify examples of the use of transgenic species and use available evidence to debate the ethical issues arising from the development and use of transgenic species

Ethical issue For Against
Environment and natureIs it ethical to interfere with nature?
  • Many new discoveries are considered to be threat at first but can be used to benefit society and the environment (e.g. nuclear power). It we are able to produce products that are of benefit, it would be unethical not to develop them.
  • Having GM organisms may reduce the pressure on natural ecosystems that provide food and other resources e.g. farming GM salmon reduces the risk of overfishing.
  • Is it wrong to ‘play God’ and tamper with nature?
  • Biodiversity is upset as variation in the gene pool is lowered; this may lead to mass extinctions of ‘wild’ and/or modified species.
  • If GM organisms escape into the wild, they may outcompete natural species or interbreed e.g. herbicide resistance transfers to weeds.
  • We may be changing the natural process of evolution.
  • Is it ethical to mix genetic material of humans with that of other organisms?
Financial and social justice issuesIs it ethical to put a price on genetically modified products, thereby giving only a select group access to these?
  • We could create crops that are more drought-tolerant/resistant to pests and have a higher yield; this is cost-effective since the quality improves and less money needs to be spent (e.g. on pesticides).
  • Financial gain is essential – money can be put back into further research.
  • People in third-world countries may not be able to afford or have access to beneficial GM products, so they may fall even further behind developed countries, widening the poverty gap even more.
  • Patenting and ‘ownership’ of certain genes or species – single companies have the rights to technologies; other companies do not have access to them (even if they could be beneficial), creating a monopoly.
Medical and health issuesIf we are able to make products that bring medical benefits and improve the health and quality of life for humans, would it be unethical not to do so, even if we are unsure of the consequences?
  • Foods with higher nutritional value may be developed to suppler better nutrition to people in third-world countries.
  • Reduced use of pesticides is better for consumers’ health.
  • Transgenic bacteria can be used to create useful products in medicine e.g. insulin, copies of CFTR gene for cystic fibrosis gene therapy trials.
  • Potential long-term health risks of GM products are not yet known.
  • People with allergies may have allergic reactions to food they could previously eat, if those goods include DNA of other organisms.
Animal and human rights issuesIs it ethical to genetically modify foods or other products and make them available to the public, when the public may not have full knowledge of what they are consuming or being exposed to, and they are not given alternatives and the right to choose?
  • GM crops may be used to solve good shortages in third-world countries, producing a higher yield at lower cost.
  • Vegetarians may unknowingly eat food with animal DNA.
  • Transgenic animals could be created as genetically modified ‘works or art’.
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