HSC Biology – Blueprint of Life
5. Current reproductive technologies and genetic engineering have the potential to alter the path
of evolution.
The term reproductive technology applies to any use of technology to assist and improve reproduction.
Over the years humans realised the advantage of selecting seeds from the best crops and breeding the best
quality animals, to improve the quality and yield of future generations. This is known as selective
breeding or artificial selection.

Identify how the following current reproductive techniques may alter the genetic
composition of a population:
o Artificial insemination
o Artificial pollination
o Cloning
Selective breeding techniques are reproductive technologies that may be used to achieve hybridisation.
Selective breeding can be thought of as a form of artificial selection imposed by humans, when they conduct
deliberate crosses of living organisms to obtain a combination of desirable characteristics in the offspring.
Artificial Insemination
The natural breeding or sexual reproduction that occurs in mammals can be modified by artificial
insemination (AI). This technique changed her management by altering the ‘how’, ‘when’ and ‘where’ of
the breeding.
AI involves collected semen from a selected stud animal and then introducing this semen by artificial means
into the reproductive tract of females of the same species. When first developed, the technique of AI
involved the use of fresh semen only.
The use of AI increases the number of offspring that one stud animal could produce (for a bull – up to ten
times).
In 1949, a successful technique was developed for freezing semen. Successful meant that when the frozen
semen was thawed, it contained motile sperm that were capable of fertilising eggs. The freezing technique
involves adding semen to a special solution of controlled pH and which comprises a mixture of various
chemicals, including glycerol.
AI eliminates the need for transporting large animals over long distances, is cost effective and reduces the
danger to animals of injury in transit or during mating.
Genetic Impact of AI in animal breeding
Through AI technology, physical and temporal barriers to mating are removed. This technology means that
one prize stud can:
Fertilise many more females than under natural conditions.
Fertilise females located hundreds or thousands of kilometres distant from stud animals because
its frozen sperm can be easily transported over great distances.
Fertilise female animals and produce offspring long after the death of that stud animals.
Through of AI technology and the transport of frozen semen, the genetic influence of a small number of stud
animals has been greatly extended over time and space. This influence has affected the genetic composition
of the herds concerned.
The use of a small number of stud males in a breeding program means that the genetic variation is reduced
compared with the situation that would exist if random mating occurred.
Because stud animals are chosen for their superiority in a limited number of inherited traits, several
consequences from the widespread use of a few stud animals may result including:
Specific alleles of a few selected genes will become predominant in the herd and alternative
alleles of the genes concerned will be lost.
Potentially valuable alleles may be unwittingly lost form the genetic composition of the herd
because other inherited features are ignored.
Overall, the widespread use of AI using a limited number of stud animals can result in a loss of genetic
variation from the genetic composition of that species.
1
EXTRA: Sex Manipulation
Under normal circumstances a sex ratio of about one male to one female is expected in live born mammals.
In the beef industry however, male calves are preferred because they have more beef (muscle) on their
carcasses at a given age than females. In contrast, in the dairy industry, female calves are preferred for
their milk production.
Sex selection is now possible. After semen has been collected from a stud bull, for example, it is possible
to treat the semen and separate sperms with X chromosomes from those with Y chromosomes.
Sperm cells are first labelled with a harmless fluorescent dye that binds to DNA. The X chromosome in
mammals is larger and contains more DNA than the Y chromosome. As a result, the sperm with X
chromosomes fluoresce more brightly than those with Y chromosome.
Selective Breeding in Plants – Artificial Pollination
The process of artificial pollination involves removing the stamens of a flower and dusting the pollen onto
the stigma of the same flower (self-pollination) or another flower (cross-pollination). This gives the breeder
a greater degree of control over the breeding process.
The process of artificial pollination involves:
removal or unripe stamens from the plant to be fertilised
protection of the stigma of the selected female plant from stray pollen
Collection of pollen to be used in the artificial pollination.
Transfer of the donor pollen onto the stigma of the female plant.
Genetic Impact
Along with all of the processes described for AI, the additional manipulation that artificial pollination
provides is that of the creation of new species.
In this case, pollen is collected from one species and transferred to the stigma of a second closely related
species. One example of this was the creation of a wheat-rye hybrid plant. A wheat species was artificially
pollinated using rye.
The result of this artificial pollination was a new plant species with one set of wheat chromosomes and one
set of rye chromosomes. Such a plant would be infertile because its chromosomes could not undergo the
normal pairing that occurs during meiosis.
By using a specific chemical treatment, a doubling of the chromosome number in the plant cells occurred so
that the cells then contained two sets of wheat chromosomes and two sets of rye chromosomes. As a result,
the mature plant would be fertile and undergo normal meiosis.
Artificial pollination combined with the use of chemical treatment to double the chromosome number in cells
accelerates evolution. This technique allows genetic materials from two species that would naturally have
remained reproductively isolated to be artificially combined.
Cloning
There are three types of cloning:
1. Reproductive cloning – which involves creating a genetically identical, fully developed (whole)
organism using a cell (or a few cells) from another mature organism. This whole organism
cloning is a form of asexual reproduction and so it is considered to be a reproductive technology.
2. Therapeutic cloning – which involves using cells from an individual to produce a cloned
embryo, which is then used as a source of embryonic stem cells to replace degenerating adult
tissues or to repair damage. The purpose of therapeutic cloning is not to produce a new animal
or plat, but to provide a source of cells that can be used to repair adult tissue that has been
damaged.
3. Gene cloning – occurs at a cellular level and involves producing identical copies of a gene. It is
an important step in the process of genetic engineering.
2
Some productive technologies, such as artificial insemination and artificial pollination involved the
modifications to sexual reproduction that occurs in animal and plant populations. These technologies
restrict the source of sperm or pollen to that from selected animals and plants and use artificial means to
transfer the selected sperm and pollen to the reproductive structures of females.
Cloning involves methods of asexual reproduction in which genetic information of the new organism
comes from one ‘parent’ cell only.
The cloning of mammals involves:
obtaining the nucleus from a somatic (body) cell of an adult animal – this is the ‘donor’ nucleus
Removing the nucleus from an unfertilised effect cell, typically of the same species – this is the
enucleated egg cell.
Transferring the donor nucleus into the enucleated egg cell.
Culturing the egg cell and donor nucleus until embryonic development begins.
Transferring the developing embryo into the uterus or a surrogate animal where it completes
development.
The genetic information in the cloned animal comes from the nucleus of the adult body cell, and so the
genotype of the cloned animal is determined by the donor nucleus and not by the egg in which the nucleus
is transferred.
The success rate for initiating development of the egg cell after transfer of the donor nucleus is low.
Cloning Plants
Cloning of plants occurs both naturally and artificially.
Natural cloning occurs through runners and suckers. Artificial cloning of plants involves cuttings and the
culturing of a piece of adult plant. As this piece grows, it can be further subdivided so that a large number of
genetically identical plants can be produced from the original piece.
If large numbers of plants are produced through natural or artificial cloning, the members of the resulting
population are genetically identical. As a result, these populations have very limited genetic variation
compared with a population that is has been produced by sexual reproduction.
Reproductive cloning produces an organism derived from only one parent. It produces organisms that are
genetically identical. If many clones are produced from one parent organism, the effect would be to reduce
the variability of the population as all organisms would have identical DNA. Cloning is used as a form of
selective breeding once an ideal hybrid has been obtained. The advantage is that cloning reduces the
unknown element is selective breeding – the characteristics being bred can be precisely controlled. This type
of artificial selection occurs in growing seedless grapes and bananas.
In nature, genes are conserved by evolution only if they serve an essential function for the organism. The
disadvantage of cloning is that is if all members of a species are identical, the population is less likely to
survive sudden environmental changes and would be vulnerable to foreign pathogens.
There is evidence that each time a mammalian cells divides, the specialised ends of its chromosomes lose
some DNA base pairs and become shorter. These ‘ends’, which are known as telomeres, do not carry
structural genes. Sientists suggest that the shortening of the chromosome ends is associated with ageing.
Advantages of Genetic Engineering
Plants:
-
Crop Improvement: New crop varieties with higher protein levels and the ability to withstand
some harsh environmental conditions
Pest and herbicide resistance: Crops engineered for insect resistance so the use of
insecticide is reduced
Extending the shelf life of produce: Delaying the natural process of ripening in tomatoes
Animals:
-
Livestock Improvement: Sheep have been modified to enhance wool production. Cows are
being treated to produce more milk.
Transgenic bacteria: Plasmids in bacteria are now widely used to produce hormones or
proteins e.g. insulin production by recombinant E. coli
Animal models used to test human disease: Transgenic mouse with HD gene. Transgenic
flies used to test genes affecting human growth.
3
Restriction Enzymes and Plasmids
Genetic engineering was made possible by restriction enzymes and plasmids found in bacteria. Plasmids in
bacteria are small circular DNA molecules separated from chromosomal DNA which replicates independently
of chromosomal DNA. This ability makes it possible for bacteria to replicate any new DNA that may be
inserted into it artificially.
In bacteria, restriction enzymes cut up invading DNA that is injected into the bacterial cells by viruses that
parasitise bacterium, known as bacteriophages. Restriction enzymes are specific, will recognise short
sequences of DNA and cut both sides of the double stranded DNA. There are hundreds of restriction enzyme,
each one recognising a different sequence of DNA. Those restriction enzymes that are useful cut the DNA
and expose nitrogen bases are called sticky ends. Once base pairing occurs, the DNA sequence is stuck
together by an enzyme known as DNA ligase. Using the qualities of restriction enzymes and plasmids,
human insulin grown in bacteria can be mass-produced for diabetics.
How to clone a human gene
1. Remove the plasmid DNA from bacteria. Remove DNA from human cells that contains the gene
you are interested in – e.g. insulin
2. Cut the DNA bacterial plasmid and in the human chromosome with the same restriction enzyme.
This will result in many fragments of human DNA.
3. Mix the plasmids of DNA with the many DNA human fragments. Add DNA ligase to paste the
sequences together – recombinant DNA is hence formed.
4. Put new plasmids in a culture of bacteria. Some bacteria will take up the plasmid DNA carrying
gene of interest. Other bacterial cells will take up non-recombinant plasmids, plasmids with
different DNA. These can be separated. The bacteria with the gene of interest are harvested.
5. Researchers can then either make copies of the gene and harvest them, or allow the cultures
carrying the human gene to make the protein.
4

Describe a methodology used in cloning
Reproductive cloning is known as somatic cell nuclear transfer [SCNT]. Each time a mammal is cloned, the
process (SCNT) involves three animals: one that donates the nucleus, one that acts as an egg donor and
one that plays the role of surrogate mother.
Ian Wilmut and his team used the method of SCNT to create Dolly the sheep:
1.
Cells were taken from the udder (mammary glands) of a six year old ewe. They were
starved of nutrients to stop them dividing.
2.
The nucleus was removed from an unfertilised egg, a process called enucleation, of
another sheep [2]. The scientists made sure the rest of the cell (the cytoplasmic contents
and membrane) was in good working order.
3.
An udder cell from sheep 1 was injected into the enucleated egg of sheep 2. The two cells
were then zapped with electricity, which cause the cells to fuse together and the now
fertilised egg cell was allowed to undergo normal growth and development by the process
of mitosis. As the cells continued to divide, the embryo was implanted into the uterus of a
third sheep. The embryo continued to grow and was born as a genetic identical twin to
the first sheep – the original sheep that donated from its mammary gland.
5

Outline the processes used to produce transgenic species and include examples of this
process and reasons for its use
Biotechnology is any technique that uses living organisms to make products. As far back in recorded
history as biblical times, biotechnology was used – e.g. yeast was used to bake bread for the fermentation
of wine and the production of cheese.
In modern times, biotechnology has come to be associated with genetic modification/engineering of
living organisms. Modern biotechnology involves the manipulation of living organisms to artificially combine
specific qualities of different organisms. Genes can be removed from the cells of one organism and inserted
into the genome of another where they become part of the new organism’s genetic make-up and are passed
onto its offspring. This has only become possible with an advance in the scientific understanding of the
structure and functioning of DNA.
A transgenic organism is one whose normal genome has been altered by introducing a gene from another
species (transgene) into it in such a way that the organism can pass on this transgene to its offspring during
reproduction.
The creation of transgenic species has many applications including:
Creating genetically modified foods with increased nutrients, higher yields and which can be
processed more easily.
Introducing resistance to disease, pests and pesticides in species
Treating disease
Reproductive technology
Note:
Transgenic: A transgenic species is one that has been created by moving a gene across a species –
i.e. gene collected from one organism and inserted into the DNA of another [hence becoming inheritable].
This involves inserting the gene into a ‘germ-line’ cell – a cell that will give rise to new offspring. The gene
should be inserted into a fertilised eff cell that gives rise to an organism.
Gene Therapy: A healthy copy of a gene in inserted into defective tissue only. Therefore it will not
be passed onto the next generation. Gene therapy will be used as a new form of medicine, to replace
conventional treatments for diseases; the desirable gene will be inserted into a non-germ line tissue in a
developed or mature plant/animal.
How to Produce Transgenic Species
The process of Gene Manipulation
1. Cutting: A gene for a favourable characteristic is removed from the cell of an organism, using
restriction enzymes. This can be done using three methods:
a. Isolating the gene from chromosomal DNA
b. Chemically Synthesising it from nucleotide sub-units
c. Making a copy of it from a template
2. Copy: Multiple copies are made [called gene cloning] – this step is usually carried out in bacteria.
3. Paste: The genes are inserted (injected) into an egg cell of another species after fertilisation
becomes a part of the newly formed organisms DNA.
4. The egg develops into a mature organism (transgenic species) with the new gene ‘switched on’ to
function.
Gene Delivery Techniques
1. Micro-injection of DNA directly into the nucleus of a single cell – this is usually performed under an
optical microscope to introduce DNA into egg cells when creating transgenic species.
2. Biolistics: Methods of mechanically delivering DNA on microscopic particles into target tissues and
cells by ‘firing’ them from a gene ‘gun’; e.g. tiny gold particles are used to coat the DNA, which is
then fired at the target cells under high pressure or voltage by a gene gun.
3. Electroporation: Increasing the membrane permeability by applying an electrical current.
4. Transduction by a viral vector: DNA may be carried by vectors such as liposomes or bacterial
plasmids into cells. These viral vectors may be injected directly into the bloodstream or may be
delivered by aerosol.
6
Assessing whether the gene has been incorporated
A gene for a fluorescent protein from jellyfish is used to determine whether an individual has successfully
incorporated the transgene. The fluorescent gene is used as a marker and is attached to the desired gene
that will be inserted into the prospective transgenic organisms. The gene with attached marker is injected
into an egg cell and the resulting offspring fluoresce under certain lighting conditions. This allows the
biologist to recognise immediately which individuals have been transformed.
Detailed Example – Bt cotton plants
Reasons for the production of transgenic cotton:
-
Traditional pesticides used on cotton had to be made stronger and more frequently applied to
eradicate insect pests such as the caterpillar. With increased sprayings these caterpillars were
building up immunity to the pesticides due to natural selection. Bt cotton plants were genetically
modified, as a result, in order to contain a gene that codes for the production of a protein that
kills the caterpillar. The insertion of the Bt gene into the cotton plant has reduced the need to
use pesticides to kill these caterpillars, which is better for the environment and reduces the
development of pesticide resistance in caterpillars. This gene is called Bt because it was
originally taken from the soil bacterium [Bacillus Thuringiensis]. While common cotton growers
in NSW and Qld would normally spray their crops numerous times in one growing, now they only
spay occasionally to eliminate sucking insects and mites, using a narrow spectrum pesticide that
does not wipe beneficial insects such as ladybirds.
-
The Bt gene codes for the production of the toxic protein in an inactive form that is harmless to
humans and most animals. However, when the protein is eaten by the caterpillar, it is converted
by the digestive system into an active form that kills the insect.
Process used to produce transgenic cotton
1. Scientists cut normal cotton seedlings into small pieces and place them on a solid growth medium
where they grow into calluses. After about six weeks, they transfer the callus cells to a liquid
medium where they are given hormones to induce them to grow into cotton plant embryos.
2. By genetic engineering, the Bt gene is extracted from the Bt bacterium using restriction enzymes.
3. The Bt gene must then be transferred to the cotton plant embryos. This is done using a second
bacterium as a vector [Agrobacterium tumefaciens]. This vector is able to inject genes into other
cells.
4. The cotton plant embryos are dipped in a solution that contains the vector combined with the Bt
genes. The vector bacteria then inject the Bt genes into the cotton cells.
5. Once the gene is inserted, the embryos containing the Bt genes are grown in tissue culture and are
then germinated into small plants, which are planted in pots and grown in glasshouses. These plants
are now a transgenic species, containing a gene from another species in their genome.
7

Identify examples of the use of transgenic species and debate the ethical issues arising
from the development and use of transgenic species
Examples of Transgenic Species
1) Transgenic sheep in Australia have been given a gene for the blood-clotting factor lacking in
people who suffer from haemophilia. The factor can be obtained from the sheep’s milk and
used for human treatment.
2) The alfalfa plant in Australia has been genetically modified to produce high levels if cysteine.
Sheep that graze on this alfalfa with high levels of cysteine have an enhanced wool quality.
Future research involves trying to develop a method to insert this gene directly into sheep.
3) Golden rice with high levels of beta carotene was created using A. tumefaciens and the
genes that increase the vitamin A production. This golden rice could help prevent vitamin A
deficiency that leads to blindness in many areas of the world.
4) Soya beans are one of the major food crops that have been genetically engineered to
contain a gene that confers resistance to the herbicide known as Round-Up. The gene
produces an enzyme that neutralises the active ingredient in the Roundup herbicide. Plants
containing this gene can be sprayed with this herbicide and are unaffected; in contrast with
other plants, including weeds, which lack the gene, and are hence killed.
5) Zebra-fish were the first genetically engineered pets. Normally black and silver, they
fluoresce or glow red in the dark because of a gene for bioluminescence form coral that
scientists transplanted into their embryonic DNA. These were also developed to detect the
presence of toxins that are carcinogenic.
Arguments for and against Genetically modified Food:
Arguments in Favour
Arguments against
Genetically modified food is rigorously tested
Technology is too ‘new’ to ensure no future problems
No need to separated modified/unmodified food
because very little has been changed within crops
Other techniques are available – hence no need to
use genetically modified food
The impact of modified crops on the environment
has been carefully assessed.
As modified and unmodified crops are being mixed
together, we are not given a choice between them
All genes have the same building blocks and only
copies of genes are used.
Weeds may become genetically resistant to weed
killers
It is a quicker and more accurate development than
selective breeding.
Uncontrollable genetic pollution may occur
Adding one gene is only a tiny change in the overall
genetic makeup and modified plants can be
thoroughly tested.
Natural plants and animals may be disadvantaged
GM foods can be fully labelled
Genetic modification is tampering with nature
Tiny alterations to genes may have radical
consequences
8
Ethical Issues:
Biotechnology and its applications have a significant impact on everyday life in today’s world. Genetically
modified plants and animals are common in agriculture, genetically modified food is commonly found on our
supermarket shelves and genetic testing is becoming a routine part of medical practice and forensic
investigations. Biotechnology is the new and controversial global revolutions — we need to judge carefully
what boundaries are being crossed if we allow unregulated manipulation of genomes. The possible future
outcomes of the development and use of transgenic species must be assessed. There are many advantages
and disadvantages of this new technology.
As knowledge and technological power in the biological sciences advances rapidly, the need arises for careful
consideration of the values in society that are at stake. An International Bioethics Committee has been
formed by UNESCO to ensure that progress in genetics is accompanied by reflecting on and taking action to
ensure the values of human dignity and freedom are respected. Respect for all living organisms and the
environment is encouraged. They are also concerned with trying to reach international agreement on legal
and ethical issues in molecular biology.
Areas for consideration when assessing the impacts of biology on society and the environment
1.
2.
3.
4.
Effects on the environment
Financial and social justice issues
Medical and health benefits
Animal and human rights.
9

Discuss the impact of reproductive technologies on the genetic diversity of species using a
named plant and animal example that have been genetically altered.
Cloning
Cloning decreases the genetic diversity of a species as the offspring produced are genetically identical to the
parent. This can be seen in the case of Dolly the sheep, whose genetic material was identical to that of the
donor sheep from which it came. In the case of cloning, if new selective pressures arise, all the organisms
will not possess characteristics to combat the pressure as all are genetically similar, hence the species could
be wiped out.
[Note: This is also a disadvantage in asexual reproduction where the offspring are identical to the parent]
Artificial Pollination
The use of artificial pollination to create hybrids is an area where genetic diversity increases—new
combinations of alleles are introduced into the gene pool of a population. For example, wheat hybrids were
created by crossing Purple Straw variety and a Fife–Indian wheat variety Yandilla to create a new variety
called Federation. New gene combinations can be passed on to future generations if the hybrids are fertile,
increasing their frequency in the gene pool and thereby altering the genetic composition of the population.
Distantly related organisms are less likely to have mutations of the same alleles and therefore offspring
have less chance of being homozygous recessive for any pair of alleles.
An interesting case of artificial pollination being used to create a new species is the example of a wheat–rye
hybrid that was produced by crossing a wheat species, Triticum turgidum, with a rye plant, Secale cereale,
to create the hybrid cereal, Triticale. Usually, hybrids created from two different species are sterile because
they have a difference in chromosome number and during gamete formation their chromosomes cannot pair
up during meiosis. The triticale hybrid was subjected to a chemical treatment that caused its chromosome
number to double, making the new species tetraploid— that is, it has four sets of chromosomes rather than
being diploid, with two sets. Its chromosomes can now pair and separate during gamete formation and so it
is fertile. These hybrids are no longer able to interbreed with the wild diploid species—a form of reproductive
isolation exists, equivalent to a new species arising in nature due to isolation. Therefore hybridisation by
artificial pollination can increase genetic diversity by creating new species. In the long term, ongoing
breeding of this same species may lead to a decrease in genetic diversity.
Advantage—increased genetic variety
When new hybrid species are created, this leads to a short-term increase in genetic diversity and may result
in hybrid vigour: hybrids are healthier organisms because most do not have two copies of detrimental
(harmful) recessive alleles. Greater genetic diversity within the gene pool equips a species for adaptation
and survival if there is a sudden environmental change such as an epidemic disease or food shortage.
Disadvantage—decreased genetic variety
In the longer term, the continued breeding of the same hybrid lines decreases genetic diversity. The overuse
of one breeding line, or ‘in-breeding’ of hybrids from the same parental lines, leads to a greater chance of
the offspring inheriting two copies of the same detrimental allele from their closely related parents. They are
also less likely to survive sudden environmental change or pathogens.
Artificial Insemination
Similar to artificial pollination, artificial insemination can temporarily increase the genetic variation of a
population but if prolonged periods of insemination (using the same or similar donors) will lead to a loss of
alleles from the gene pool and hence decrease genetic variation.
An example of this can be seen when stud animals (typically bulls or stallions) are used to artificially
inseminate females of the same species in the hope that the offspring display hybrid vigour.
Because stud animals are chosen for their superiority in a limited number of inherited traits, several
consequences from the widespread use of a few stud animals may result including:
Specific alleles of a few selected genes will become predominant in the herd and alternative
alleles of the genes concerned will be lost.
Potentially valuable alleles may be unwittingly lost form the genetic composition of the herd
because other inherited features are ignored.
Overall, the widespread use of AI using a limited number of stud animals can result in a loss of genetic
variation from the genetic composition of that species.
10
Transgenic Species
This is only considered a reproductive technology if it increases the breeding success of the individuals.
Creating transgenic species enables scientists to choose the traits that they want expressed and to
artificially combine these qualities relatively quickly – these may affect the organisms breeding.
For example: Larger male salmon [who have been given the human growth hormone] are more attractive to
females and therefore have an increased chance of mating and passing on their genes for the large
phenotype. The potential impact on genetic diversity depends on how well the species competes in the wild.
If their genes are advantageous to the population, the frequency of these genes in the gene pool will
increase.
Advantages and Disadvantages of transgenic species
In the short term, creating transgenic species increases genetic diversity – genes are removed from one
species to another and this can be used to confer resistance on species that previously were susceptible to
particular diseases, allowing them to survive and pass on their favourable genes.
However, in the long term, it may decrease genetic diversity since the original genetic material of some
organisms may be reduced or lost forever; that is, there may be loss of biodiversity.
11