Blueprint of Life – Syllabus notes

Evidence of evolutionThe impact of evolution on plants and animals:

Some organisms have characteristics that better suit them to surviving and reproducing in their environment than other organisms.

- Changes in physical conditions: These include natural conditions, such as temperature and the availability of

water. As Australia drifted north over the last 20mil years, the climate has become more seasonal, drier and hotter.

- Changes in chemical conditions: Chemicals that can affect the evolution of species include salts and elements

such as iron. The pH of an environment can be critical to functioning of enzymes, metabolism and therefore survival.

- Competition for resources: Occurs within and between species. Resources can include food, space or

mates. If populations that live in the same area could specialise on slightly different resources or breed at different times, they could avoid direct competition.

Changes in a species resulting from environmental changes: Climate change causes changes in vegetation and this drives evolutionary

change in animals. About 10mya, Australia began drying out and rainforests in central Australia gave way to eucalypt forests, mulga woodlands and grasslands.

Open grasslands required animals that could move fast. As a result, of the drying out of the continent, some kangaroo species increased in distribution and abundance.

Areas of study supporting the theory of evolution:- Paleontology:

The study of fossils. The fossil record provides a time line of evolution of life engraved in the order in which the fossils appear in rock layers. Some parts of the fossil record show a gradual change in life forms over millions of years.

Transitional fossils provide further evidence for evolutionary change. An example is the Archaeopteryx – a bird-like reptile with wings, reptilian teeth and a long jointed tail.

- Biogeography: The study of the distribution of organisms over the Earth. Both Darwin and

Wallace observed the distribution of species in different biogeographic regions and saw this as major evidence to support the theory of evolution.

Darwin proposed that migration and evolution were much more satisfactory explanations for the unique flora and fauna in places such as Australia.

- Comparative embryology: There is an obvious similarity between embryos of fish, amphibians, reptiles,

birds and mammals. A comparison of embryos or vertebrates shows that all

have gill slits, even though thy do not remain later in life (excluding fish). This supports the idea of a common ancestor.

- Comparative anatomy: Anatomical structures on different organisms that have the same basic plan

but perform different are called homologous structures. These particular structures are evidence for evolution. The structures are shared by related species because they have been inherited in some way from a common ancestor.

An example of a homologous structure is the pentadactyl limb found in amphibians, reptiles, birds and mammals. The basic plan consists of one bone in the upper limb, two in the lower limb leading to five fingers or toes.

- Biochemistry: Some biochemical processes are the same for all living cells. Certain proteins

are commonly found in a large number of organisms. Chemical tests of blood proteins have been used to slow biochemical similarities or evolutionary differences between animals. Closely related species have few differences in DNA. Humans and chimpanzees have only about 1.0% difference in DNA.

The structure of vertebrate limbs: All vertebrate limbs have the same homologous structure – the pentadactyl

limb. They all have a humerus, radius and ulna bones. The proportionate length of these bones varies, along with the wide-ranging purposes, including swimming, flying and walking. This pattern of similarity suggests common ancestry.

In bats, the limb is modified to form a wing with the fingers extended and skin stretched between each finger. Whales have within their single paddle-like fin a fully formed pentadactyl limb.

Darwin/Wallace theory of evolution by natural selection and isolation accounts for divergent and convergent evolution:

Natural selection states that those organisms that have characteristics that best suit them to their environment will survive, reproduce and pass some of those characteristics on to their offspring.

In any population of sexually reproducing organisms, there are large variations of inheritable characteristics. If several groups of the same species become isolated, the environments in which the groups are isolated may result in the selection of different characteristic.

If the differences are great enough, the groups will not be able to interbreed to produce fertile offspring (adaptive radiation). This can lead to both divergent and convergent evolution.

- Divergent evolution: Occurs when closely related species experience quite different environments

and as a result vastly different characteristics will be selected. Marsupials in Australia radiated widely reducing competition for resources by occupying different niches and often developing specialised diets. The diversification of the pentadactyl limb is divergent evolution.

- Convergent evolution: Occurs when two relatively unrelated species develop similar structures,

physiology or behaviours in response to similar selective pressures from similar environments. Dolphins (mammals) and sharks (cartilaginous fish) have evolved a streamlined body shape and fins that enable them to move efficiently in their aquatic environments, yet they are only remotely related as vertebrates.

Modeling natural selection: Aim: to carry out an activity that models the processes of selection of the

‘most fit’ organisms. Method: a simple simulation model of natural selection can be carried out

using colourful lollies. You simulate natural selection by your group taking one lolly and eating it, then count and compare the number and colour of lollies remaining.

Conclusion: in our experiment, the taking of purple, blue and red lollies simulates successful models of natural selection. The remaining colours of yellow, orange and green would reproduce and carry on their genes, being the ‘most fit’ organisms.

Technology advancements that have changed scientific thinking about evolutionary relationships:

Advances in the analysis of DNA base sequences and computer processing of results have improved our understanding of whale evolution.

It was believed that whales descended from land mammals that had returned to the sea. Anatomical and paleontological evidence suggested the whales’ closest living land relatives were the even-toes hoofed mammals such as modern cattle or sheep.

DNA sequences that transcribe the milk protein beta-casein and kappa-casein have been compared and have confirmed this relationship and suggested that the closest land-bound living relative of whales may be the hippopotamus. In this case, molecular biology has amplified the fossil record.

How the theory of evolution has developed: By the beginning of the 19th century, a great deal of evidence was available to

the scientific community that supported evolution. What was missing was a plausible mechanism to explain how evolution was occurring.

Charles Darwin and Alfred Wallace independently arrived at evolution as a result of natural selection. By the early 1840s, he had documented the main points of his theory - that those organisms that have characteristics that best suit them to their environment will survive, reproduce and pass some of those characteristics on to their offspring.

Eventhough the Darwin/Wallace theory of natural selection caused uproar amongst Victorian society in England when published, scientific thinking was gaining respectability and becoming an important mechanism for change.

The theory of evolution has encountered opposition since it was first introduced. This is because it was seen as a threat to religious and social beliefs.

The work of Gregor Mendel:Experiments by Gregor Mendel:

In the 1860s, he formulated the principles of genetics by careful and methodical experimentation with garden peas. Mendel chose peas for his breeding experiments because:

o The plants ‘bred true’ for the characteristics he studied. He could establish a true-breeding stock for contrasting characters.

o Garden peas can ‘self-fertilise’. The parents could be artificially pollinated to produce the first generation (F1). These offspring could be self-fertilised to produce the second generation (F2).

Mendel’s explanations of his results are:o Inheritance is not a blending of characteristicso Inheritance is controlled by a pair of particles in the cells which he

called factorso These two factors segregate from one another when sex cells are

formedo Characteristics are either dominant or recessive

Mendel’s experimental techniques:Mendel was successful because he:

Used peas, which were easily grown and produced successive generations rapidly

Selected easily observable characteristics Strictly controlled the fertilisation process Used mathematics rigorously to analyse his results Studies traits that had two easily identified factors

Monohybrid crosses involving simple dominance: Monohybrid crosses involve looking at one characteristic only. For example, a cross may involve a true breeding (homozygous) tall plant

crossed with a true breeding (homozygous) short plant. This produces a first generation where all of the plants are tall.

Mendel explained the first generation trait as the dominant factor, thus Mendel was able to explain his observed ratios.

o F1 – all tallo F2 – 3 tall: 1 short

Punnett squares: A monohybrid cross involves the inheritance of one characteristic. All

problems apply Mendel’s basic laws of inheritance. In genetic problems, genes are labelled with a capital letter (T) for the

dominant gene and a small letter (t) for the recessive gene. Punnett squares can be used to predict the genotype (the gene pair make

up) and phenotypes (appearance) of offspring. EXAMPLE: Mendel’s pea plant experiment

In the sample problem, a homozygous tall plant (TT) is crossed with a heterozygous tall plant (Tt), By filling in the squares, it is possible to work out all of the combinations that are likely to occur.

When you analyse the information in this case, you can predict that 100% of the offspring will be tall plants: 50% are homozygous tall (TT); 50% will be heterozygous tall plants (Tt).

Homozygous and heterozygous genotypes in monohybrid crosses: A genotype is the type and arrangement of genes. A phenotype is what the organism will look like as a result of the genotype If the alleles are the same, they form a homozygous genotype. A pure

breeding organism is homozygous for that characteristic (e.g. TT) If the alleles are different, they form a heterozygous genotype. A non-pure

breeding or hybrid organism (Tt) is heterozygous.

Alleles and genes: An allele is an alternative for a particular inheritable characteristic, e.g. tall (T)

and short (t). Humans can have A, B or O alleles for blood type. With the development of modern genetics, we now identify these factors as genes.

A gene is part of a chromosome. Genes determine the inherited characteristics of an individual. Chromosomes and genes occur in pairs. The different forms of a gene that occur on the same place on matching chromosomes are called alleles.

Pedigrees or family trees: Pedigrees or family trees are simple ways of describing how characteristics

are inherited for several generations. The diagram uses a set of standard symbols (e.g. circles females, squares

males, offspring are shown in order from left to right). A line represents a union, and a line down indicates offspring from the union. Filled in symbols represent individuals displaying the phenotype being studied.

Pedigree guidelines: If a trait skips a generation, usually it is recessive If there’s only a few examples of a trait, usually it is recessive If a trait is exhibited in a particular sex, usually it is sex linked If a trait is exhibited in the children but not the parents, usually it is recessive If a trait occurs frequently, probably dominant

Current use of pedigrees: Pedigrees are valuable tools in genetic counseling. It allows a pattern of

inheritance to be traced throughout generations of a family. This can allow identification of the genetic disease and advice can be made available on the probability of a couple having an affected child.

Examples of genetic diseases include cystic fibrosis (recessive genetic disease) and Huntington’s chorea (dominant genetic disease)

The relationship between dominant and recessive alleles and phenotype: Phenotype is the visible appearance of the genetic factor (genotype).

Phenotype is what the offspring will look like and/or what chemical or behavioural characteristics it will have.

Mendel found that the individual in the F1 generation usually showed one of the parent’s characteristics or traits. Mendel called the character or trait that appeared in the F1 the dominant characteristic. The one that did not appear in the F1, he called the recessive characteristic.

Dominant alleles will be expressed as the phenotype an organism with the genotype TT or Tt will be tall.

Recessive alleles will be expressed as the phenotype when the organism is homozygous the genotype tt will be expressed as short

Hybridisation within a species: Hybridisation is the process of crossbreeding different organisms.

Hybridisation within a species occurs between different identified types or strains. Hybrid corn is one example of hybridisation.

The reason for carrying out hybridisation: The purpose of the hybrid is to produce a plant that has a more beneficial

combination of alleles than its true breeding parents. Hybrid corn grows more vigorously, resists disease and insect pests, tolerates stress more effectively and stands upright better. It therefore produces greater crop yields.

The recognition of Mendel’s work: Mendel began his work in 1858 and published the results of his experiments

in 1866, but his work lay undiscovered until 1900 when others performed similar experiments. It was only then that the importance of his work was realised.

It is unclear why such original work went unnoticed, perhaps:o Mendel was not a recognised, high profile member of the scientific

communityo He presented his paper to only a few people at an insignificant, local,

scientific meetingo Other scientists did not understand the work or its significance

Chromosomal structureThe work of Sutton and Boveri on chromosomes:

Two scientists are credited with the discovery of the role of chromosomes in 1902. They were the German scientist Theodor Boveri and the American microbiologist Walter Sutton

Boveri worked on sea urchins and showed that their chromosomes were not all the same and that a full complement was required for the normal development of an organism

Sutton worked on grasshoppers and showed that their chromosome were distinct entities. He said even though they duplicate and divide, they remain as a distinct structure. He associated the behaviour of chromosomes with Mendel’s work on the inheritance of factors and concluded that chromosome were the carriers of hereditary units.

Together, their work became known as the Sutton-Boveri chromosome hypothesis

The chemical nature of chromosomes and genes: Chromosomes consist of 40% DNA and 60% protein. Short lengths of DNA

make up genes so genes have the same chemical composition as DNA.

The structure of DNA: DNA is a nucleic acid in the shape of a double helix. Each strand of the helix

consists of four different nucleotides made up of deoxyribose sugar, a phosphate molecule and a nitrogen base.

The helix is like a twisted ladder. The backbones of the structure (sides of the ladder) consist of the deoxyribose sugar and the phosphate molecules. The bases form the rungs between the sides of deoxyribose sugar and phosphate molecules and are complementary (only pair with their matching bases)

Adenine thymine, guanine cytosine Each nitrogen base code carries a set of instructions for controlling

inheritance and all the chemical processes that will occur in the cell. A gene controls the putting together of amino acids to make proteins. Amino acids are the building blocks of proteins.

The structure and behaviour of chromosomes during meiosis and the inheritance of genes:

Meiosis is cell division that produces sex cells and halves the number of chromosomes.

The genes are located on the chromosomes. They are duplicated during the first stage of meiosis and are then randomly assorted depending on which chromosome from each pair enters which new haploid cell during the first and second division.

Since the chromosome pairs carry different genes, the daughter cells (sex cells) produced by meiosis are almost always genetically different.

The role of gamete formation and sexual reproduction in variability of offspring:

Gamete formation results in the halving of the chromosome number (n) (diploid to haploid) and sexual reproduction results in combining gametes (haploid to diploid) to produce a new diploid organism (2n). These processes produce genetic variation.

During meiosis, chromosome pairs sort themselves independently and randomly. This is called random segregation, which produce genetic variation.

In sexual reproduction, each female or male cell produces 4 sex cells (gametes) from the process of meiosis. Each of these sex cells is haploid (has half of the normal chromosome number) and has a random assortment of genes from the parent.

The genes (Mendel’s alleles) are separated and the sex cells have a random assortment of dominant and recessive genes. More variability is introduced depending on which sex cells are successful in fertilisation. The resulting embryo has a completely different set of genes from either of the parents.

The inheritance of sex-linked genes and alleles that exhibit co-dominance: The inheritance of sex-linked genes involves genes being carried on the X

chromosome and therefore linked to the sex of the offspring. In some species, males only have one X and the Y has no equivalent genes. In humans, 22 pairs of chromosomes are equal but the sex pair XX or XY is unequal.

These do not produce simple Mendelian ratios because the gene will be expressed in species in which males only have one X, irrespective of whether the allele is dominant or recessive.

The inheritance of alleles that exhibit co-dominance involves both alleles being expressed in the heterozygous offspring.

These do not produce simple Mendelian ratios because there are three possible phenotypes.

Colour blindness is an example of a gene that occurs on the X chromosome. Males do not have a matching part of the Y chromosome to mask the gene.

The work of Morgan on sex linkage: Thomas Morgan worked on the fruit fly. He looked at crosses between red-

eyed and white-eyed flies and found that simple Mendelian crosses could not account for his results.

His work involved producing mutant varieties of fruit fly and crossbreeding them. The white-eyed mutant tended to be expressed more in males than females. He showed that some genes were sex-linked because they were located on the X chromosome. All genes that are on the X chromosome are said to be sex linked.

Homozygous and heterozygous genotypes and the resulting phenotype in examples of co-dominance:

If an individual has two different alleles (heterozygous) for a characteristic, then often one will be dominant while the other is not expressed and it said to be recessive. In some cases however, both alleles are expressed in the phenotype and the two alleles are said to be co-dominant. In this case both alleles are labelled with upper case letters.

Example – the coat colour of Shorthorn cattle: These animals have an allele for both red and white hair. As neither is

dominant, cattle with both alleles have a mixture of red and white hairs scattered over their bodies and are called roan.

Red cattle have the alleles RR while white cattle have WW. In the first generation (F1), all of the offspring will be roan (RW).

When the roan cattle are crossed, half the offspring with roan while a quarter will be red and quarter white.

The effects of environment on the expression of genes: The features that an organism has, such as its size and shape, are not only

controlled by its genes, but also by the environment in which it lives. Factors I the environment, such as the availability of water, nutrients and

sunlight, the type of soil, the presence of poisonous substances and competition from other organisms, determine how well the gene is expressed.

R R

W RW RW

W RW RW

R W

R RR RW

W RW WW

The structure of DNADNA replication:

During the ‘resting phase’, when the cell isn’t dividing, the DNA must undergo replication. Replication is the process of forming an identical copy. Enzymes play an important part in helping DNA to make an identical copy of itself.

DNA replication process: The DNA double helix is unwound by an enzyme The DNA unzips forming two single strands Nucleotides are added to the single strands resulting in two identical strands

of DNA. Why DNA replication is important:

DNA replication is essential for the completion of the steps that occur in both mitosis and meiosis. These cell divisions support growth, repair and reproduction.

Early in cell division, the chromosomes replicate and form two chromatids. For this to occur, the genes along the length of the chromosome must have also replicated. This can only occur because the structure of the DNA molecule makes exact copying possible.

The importance of replication is the exact copying of DNA so that identical, healthy offspring cells can be produced in mitosis.

Contributors to the discovery of the structure of DNA:Scientist Role in determining the structure of

DNAJames Watson and Francis Crick Suggested the double helix

structure of DNA. Also suggested the paring of the

bases (A-T, C-G), suggesting that this pairing made a way for DNA to replicate itself

Rosalind Franklin Provided the crucial scientific evidence upon which Watson and Crick based their double helix model.

She went on to apply the technique to DNA fibres obtained by Wilkins.

Sexism was rife in science at this time and Franklin struggled to be respected for her work. Failure to collaborate with her slowed progress.

Maurice Wilkins Interested in the structure of large molecules and supplied the X-ray diffraction patterns that made it possible for Watson and Crick to build the model of DNA.

In 1962; Watson, Crick and Wilkins won the Nobel Prize for physiology or medicine. Franklin had died four years earlier and so couldn’t share the prize.

The process by which DNA controls the production of polypeptides: Polypeptide synthesis involves a type of nucleic acid, called RNA (ribonucleic

acid). RNA is the intermediary between DNA and polypeptide synthesis. It is a single strand of nucleotide bases. It has ribose sugar and the nitrogen base thymine is replaced by uracil, which bonds with adenine.

There are two types of RNA that are involved in polypeptide synthesis, messenger RNA (mRNA) and transfer RNA (tRNA).

The process: In the nucleus, the double stranded DNA molecules unzip and the DNA code

is transcribed into the single stranded mRNA molecule. The mRNA moves out of the nucleus, into the cytoplasm and attaches to the ribosome. In the cytoplasm, the mRNA is translated into amino acids.

At the ribosome, the mRNA lines up forming a template. A group of three bases, called a codon, codes for a specific amino acid. There are codes that start and stop the chain formation.

tRNA has an anticodon (non amino acid forming codon) on one end and an amino acid on the other. A polypeptide is formed as each amino acid is added from tRNA to a chain following the sequence on the mRNA.

DNA mRNA tRNA polypeptide

The relationship between proteins and polypeptides: A protein is made up of one or more polypeptides. A polypeptide is made up

of a chain of many amino acids.

Beadle and Tatum’s ‘one gene – one protein’ hypothesis: Beadle and Tatum used bread mould to investigate nutritional mutations.

Using X-rays, they produced mould that was unable to produce a specific amino acid. The mould was unable to grow unless the amino acid was added.

They showed that genes controlled biochemical processes. Their hypothesis was that for each gene there was one enzyme or protein.

The enzyme that they studied consisted of one polypeptide but many enzymes consist of chains of polypeptides. Therefore, the hypothesis has been changed to the ‘one gene – one polypeptide’ hypothesis.

Mutations as a source of new alleles in organisms:

Any change in the base sequence in DNA results in changes to the polypeptides that are produced and is a source of new alleles.

To produce changes in alleles, the mutation must occur in the sex cells of the organism, which are then passed on to the next generation.

Changes in the DNA sequence links to changes in cell activity:Changes in the DNA sequences (mutations) come about when:

One base is replaced by another, for example, A instead of C causes a change in the code for the amino acid

An extra nucleotide is added to or deleted from the 3-base code sequence. If this happens, the whole sequence of amino acids is changed.

DNA breaks and a piece is inverted before being rejoined DNA sections are duplicated

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. Mutagens can be carcinogens (cancer causing) or teratogens (birth defects causing)

Environmental factors that may increase the rate of mutation include X-rays, radiation from atomic bombs and ultraviolet light

Radiation was the first mutagenic agent known. Its effects on genes were first noticed in the 1920s. When X-rays were first discovered, they were thought to be harmless and were a great novelty. Most of the first generation of scientists who worked with radiation died of cancer.

Herman Muller won the Nobel Prize in 1946 for showing that genes had the ability to mutate when exposed to X-rays. Beadle and Tatum used X-rays to produce mutations in bread mould in the formulation of their “one gene – one polypeptide” hypothesis.

The atomic bombs dropped on Hiroshima also increased the evidence for mutations caused by radiation. There was a tenfold increase in cancer deaths directly after the bombs were dropped.

DNA sequence

mRNA sequence

Amino acid sequence

Polypeptide

Cell activity

Normal beta globin sequence

ACT CCT GAG GAG

UGA GGA CUC CUC

Threonine, proline, glutamic acid, glutamic acid

Normal globin in

haemoglobin

Normal transport of oxygen

Mutated beta globin sequenceACT CCT GTG GAG

UGA GGA CAC CUC

Threonine, proline,

valine, glutamic acid

Mutated globin as occurs in sickle cell

anaemia

Reduced oxygen transportation

Mutagens may cause death in the individual but unless they affect the sex cells, the effect is not passed on to the next generation.

Part of the reason that the evidence is not clear is because sometimes the cell repairs the damaged chromosomes.

A modern example of ‘natural’ selection Insecticide resistance in insect pests is an example of ‘natural’ selection Species that lay a large number of eggs and reproduce several times in a

mating season, such as many insect species, are more likely to have offspring with a genetic mutation that can result in an adaptation for better survival.

In a natural population of insects, there are a variety of characteristics. Some insects will, by chance, be more resistant to an insecticide than others.

When the insect population is first sprayed, most of the insects will die. A few insects (those that have the most resistant genes) will survive.

These insects reproduce and pass characteristics on to their offspring – some of the offspring will inherit the ‘more resistant’ gene, some will not. The proportion of insects resistant to the insecticide will increase with each generation.

How understanding the causes of variation in organisms has provided support for Darwin’s theory of evolution:

One of the foundation pillars for the theory of evolution is the variation that occurs among individual members of a species. The basis of this variation is the genetic makeup of the individuals in a species. It is this variation that selection acts upon. Mutation of DNA provides a source of new variations thus supporting Darwin’s theory of evolution.

The concept of punctuated equilibrium and how it differs from Darwin’s view: Punctuated equilibrium states that more species adapt until they reach a

stable stage and are in a state of equilibrium with their environment. This differs from Darwin’s gradual evolution in that evolution is seen as long

periods where there is little change in organisms, followed by a shorter period where there are rapid changes.

Evolution is a sudden process rather than slow gradual change. The evidence for this comes from the fossil record where there are mass extinctions of organisms followed by the appearance of new species.

Current Reproductive Technologies:Current reproductive techniques and how they may alter the genetic composition of a population:- Artificial insemination: a reproductive technique, which uses sperm a male with desirable traits and is injected directly into a woman’s vagina or uterus. This process does require fertilisation, but not mating. This enables genes that would’ve been eliminated in natural populations to pass onto offspring, reducing the chance of the natural genetic crossovers, influencing the characteristic an organism retains. This as a result, alters the genetic composition of a population.

- Artificial pollination: the process where the pollen from a selected breed of plants with desirable traits is artificially transferred to the female stigma. Requiring fertilisation to complete the process, artificial pollination creates a new hybrid species, which alters the genetic composition of a population. The hybrid species created by these techniques create new gene combinations, meaning that some genes are more common than others. Such a process may also impede the process of natural selection and increase biodiversity.- Cloning: refers to the making of genetically identical organisms asexually from single cells, which doesn’t require fertilisation. Cloning includes both animal and plant cloning. Cloning means that populations are produced that are genetically identical to each other, altering the genetic composition of a population. The advantage to this is that desirable traits are selected and precisely controlled. His certain process is advantageous in preserving endangered species. These artificial populations however are less likely to survive sudden environmental changes as they lack the ability to adapt to such changes.

Methodologies used in cloning: One methodology used in cloning is nuclear transfer, which involves

removing the DNA from and oocyte (unfertilised egg) and injecting the nucleus, which contains the DNA required for cloning.

An example of nuclear transfer is the cloning of an animal from a cell taken from the adult. Such a process was successful in the form of Dolly the sheep. Using this method, Dolly was the first mammal to be produced using cloning techniques.

Born in 1996, Dolly was produced by fusing a mammary gland cell from a six-year-old sheep with an unfertilised egg cell, from which the nucleus had been removed. The egg then divided to form an embryo, which was then implanted into the carrier mother sheep. As a result of this process, Dolly has identical DNA to her genetic parent from which the mammary gland cell was taken.

The processes used to produce transgenic species: Scientist determine the trait they want to express, and using recombinant

DNA technology, isolate the DNA segment and transfer the genes for that trait into the reproducing cells or splice the gene into the DNA of another organism. Special enzymes then break up the chromosomes into gene fragments that represent a specific DNA sequence. The gene is then cloned. After it has been cloned, the gene is introduced into the reproducing cells of plants or animals to create the transgenic organism.

The use of transgenic species: Cloning a piece of DNA from a cholera-causing bacterium into E.coli has led to

a strain of bacteria that is used for immunization against the diseases typhoid and cholera.

Transgenic tomatoes have been developed to have a longer shelf life in the supermarkets

Transgenic field peas that contain a gene from French beans produce a protein that causes pea-eating insects to starve to death.

The ‘super-pig’ has about ten extra growth hormone genes. The genes are engineered from synthetic DNA copied from human DNA material. The genes are ‘switched on’ in the presence of zinc.

Ethical issues involved with transgenic species: Ethical issues relate to possible mistakes with the technology, the possibilities

that transgenic species could ruin the environment, as well as the rights of the animals being used and our ability to deal with the problems that might arise creating transgenic species.

An example which debates ethical issues from the development and use of transgenic species is genetically engineered salmon. To genetically engineer the salmon, the gene coding for the protein, a growth hormone is incorporated into the genes of the salmon. The salmon are then bred to be larger and faster growing fish due to the incorporation of the growth hormones in their genes.

Genetically modifying the salmon has allowed for the broadening of the gene pool, increasing the genetic diversity in ecosystems. The downside to genetically modified salmon however is that if released into the wild, the transgenic species has the ability to upset or destroy natural ecosystems, which could result in the decrease of genetic diversity.

Another example is genetically modifying potato plants. A pea gene for lectin was incorporated into potato plants. Lectin is known as a protein which interferes with digestion in insects, and termed as an ‘antifeedant’. Incorporating the protein lectin into potato plants provides protection against insect attack, resulting in the success of growing potatoes.

Like the genetically modified salmon, modifying the genetics of potato plants increases the genetic diversity. Again, concerns exist about releasing the transgenic species into ecosystems as the technology is only recent, and long-term effects have not been observed.

Reproductive technologies and genetic diversity of species:- The potential impact of reproductive technologies on biodiversity:

The potential impact of transgenic species depends on how well the species competes. If the transgenic species’ genes are at an advantage to the environment, that particular gene pool with increasingly include a greater proportion of these genes

Genes from genetically engineered organisms have the potential to move from their original release point to affect the gene pool of other plants and animals

Short term effects: genetic engineering an increase genetic diversity, as it allows genes to be moved from one species to another to produce new gene combinations

Long term effects: engineering artificial identical copies (clones) of organisms decreases the amount of genetic variation. This means that a selection of desired genes and the creation of new genetic combination can reduce the original genetic material of the organisms. This could result in the loss of the original genes.

- The potential impact using a plant example: A large US chemical company has engineered crop plants in which the seeds

become sterile before they reach maturity. Their plant growth and seed germination is dependent on applications of chemicals. The pollen from these

crops has the potential to contaminate non-engineered crops, narrowing the existing gene pool of crop plants.

Another issue surrounds the incorporation of genes, which produce natural insecticides into crops such as rice and cotton. Concerns about the impact on the genetic diversity revolve around the non-specific nature of the impact on insects and the chances if genes spreading via pollen into other plants.

- The potential impact using an animal example: Creating animal transgenic species has been less rapid then that of plants. An

example however is genetically modified fish used in aquaculture. These fish are designed for rapid growth and to attract female fish due to their increased size.

If this species of fish are released or escape into the wild, there is a high risk that their engineering genes will join the wild population, wiping out other fish populations. The creation of transgenic species through reproductive techniques such as cloning and sperm and embryo banks however has the potential to preserve threatened species.