Genetic Engineering 4.4.1 Outline the use of polymerase chain
reaction (PCR) to copy and amplify minute quantities of DNA.
Details of methods are not required. 4.4.2 State that, in gel
electrophoresis, fragments of DNA move in an electric field and are
separated according to their size. 4.4.3 State that gel
electrophoresis of DNA is used in DNA profiling. 4.4.4 Describe the
application of DNA profiling to determine paternity and also in
forensic investigations.
Genetic Engineering Aim 8: There is a variety of social
implications stemming from DNA profiling, such as identity issues
for a child who learns unexpectedly who his or her biological
father is, self-esteem problems for someone who learns he is not a
father, problems in relationships where the male partner learns
that he did not father a child, but also relief for crime victims
when those responsible for the crime are identified and convicted,
sometimes decades later.
Genetic Engineering TOK: A comparison could be made between
blood groups and DNA profiles in their potential for determining
paternity. The difficulty in assessing the chance of two
individuals having the same profile could be discussed, and also
the success of DNA profiling in securing convictions in some of the
high-profile legal cases of recent years.
Genetic Engineering 4.4.5 Analyse DNA profiles to draw
conclusions about paternity or forensic investigations. The
outcomes of this analysis could include knowledge of the number of
human genes, the location of specific genes, discovery of proteins
and their functions, and evolutionary relationships. Aim 7: Online
bioinformatics simulations are available.
Genetic Engineering Aim 8: We can either emphasize the large
shared content of the human genome, which is common to all of us
and should give us a sense of unity, or we can emphasize the small
but significant allelic differences that create the biodiversity
within our species, which should be treasured. Differences in the
success of human races in coping with the modern world and the
threat to some small human tribes could be mentioned. It is
important to stress parity of esteem of all humans, whatever their
genome.
Genetic Engineering TOK: The Human Genome Project was an
international endeavour, with laboratories throughout the world
collaborating. However, there were also efforts in some parts of
the world to gain commercial benefits from the outcomes of the
project. The data from the Human Genome Project can be viewed in
different ways: it could be seen as a complete account of what
makes up a human, if one takes a reductionist view of life, or,
alternatively, as merely the chemical instructions that have
allowed a huge range of more significant human characteristics to
develop. This could lead to a discussion about the essential nature
of humanity.
Genetic Engineering 4.4.6 Outline three outcomes of the
sequencing of the complete human genome. 4.4.7 State that, when
genes are transferred between species, the amino acid sequence of
polypeptides translated from them is unchanged because the genetic
code is universal.
Genetic Engineering Aim 8: There is an ethical or moral
question here: whether it is right to change the genetic integrity
of a species by transferring genes to it from another species. The
discussion could include the wider question of selective breeding
of animals, and whether this is distinctively different and always
acceptable. The possibility of animals suffering as a result of
genetic modification could be considered.
Genetic Engineering 4.4.8 Outline a basic technique used for
gene transfer involving plasmids, a host cell (bacterium, yeast or
other cell), restriction enzymes (endonucleases) and DNA ligase.
The use of E. coli in gene technology is well documented. Most of
its DNA is in one circular chromosome, but it also has plasmids
(smaller circles of DNA). These plasmids can be removed and cleaved
by restriction enzymes at target sequences. DNA fragments from
another organism can also be cleaved by the same restriction
enzyme, and these pieces can be added to the open plasmid and
spliced together by ligase. The recombinant plasmids formed can be
inserted into new host cells and cloned.
Genetic Engineering 4.4.9 State two examples of the current
uses of genetically modified crops or animals. Examples include
salt tolerance in tomato plants, synthesis of beta-carotene
(vitamin A precursor) in rice, herbicide resistance in crop plants
and factor IX (human blood clotting) in sheep milk. Aim 8: The
economic benefits of genetic modification to biotechnology
companies that perform it could be considered. Also mention the
possibility that harmful changes to local economies could result,
and the danger that wealth could become more concentrated in a
smaller percentage of the population if expensive but profitable
new techniques are introduced. In this respect, inequalities in
wealth may become greater.
Genetic Engineering 4.4.10 Discuss the potential benefits and
possible harmful effects of one example of genetic modification.
Aim 8: There are ethical questions here about how far it is
acceptable for humans to change other species, as well as other
ecosystems, in order to gain benefit for humans.
Genetic Engineering TOK: This is an opportunity to discuss how
we can assess whether risks are great enough to justify banning
techniques and how the scientific community can inform communities
generally about potential risks. Informed decisions need to be made
but irrational fears should not be propagated. Consideration could
be given to the paradox that careful research is needed to assess
the risks, but performing this research in itself could be risky.
Do protesters who destroy trials of GM crops make the world
safer?
Genetic Engineering 4.4.11 Define clone. Clone: a group of
genetically identical organisms or a group of cells derived from a
single parent cell. 4.4.12 Outline a technique for cloning using
differentiated animal cells. Aim 8: Ethical questions about cloning
should be separated into questions about reproductive cloning and
therapeutic cloning. Some groups are vehemently opposed to both
types.
Genetic Engineering 4.4.13 Discuss the ethical issues of
therapeutic cloning in humans. Therapeutic cloning is the creation
of an embryo to supply embryonic stem cells for medical use.
Polymerase Chain Reaction (PCR) Sometimes you only have a very
small sample of DNA. The polymerase chain reaction (PCR for short)
can make multiple copies of minute quantities of DNA very quickly.
This process is done without the need of bacteria. The sample of
DNA is repeatedly heated and cooled, in the presence of an enzyme,
DNA polymerase and nucleotides. The heating opens the DNA double
helix. The DNA polymerase attaches the nucleotides.
Polymerase Chain Reaction (PCR) Ref: Advanced Biology,
Kent
Gel Electrophoresis Gel Electrophoresis is a process used to
separate fragmented pieces of DNA according to their charge and
size. DNA is made up of a lot of repeated nucleotide sequences
(junk DNA). Around 90% of our DNA is junk DNA. The frequency of
junk repeats is characteristic for an individual, just as
fingerprints or iris patterns are unique. This pattern enables the
DNA to be exactly matched to a person. Gel electrophoresis is used
in DNA profiling.
Gel Electrophoresis DNA can be cut into lengths using
restriction enzymes. This produces fragments called Restriction
Fragment Length Polymorphisms (RFLPs). DNA is negatively charged,
so these fragments can be separated in an electric field. The
negatively charged fragments move towards the anode (positive
terminal). The smaller fragments move further than the larger ones.
This produces a banding pattern, unique for each individual.
Gel Electrophoresis Ref: Biology, Campbell
Ref: Advanced Biology, Kent Gel Electrophoresis can be used in
criminal investigations Gel Electrophoresis
DNA Profiling DNA profiling is sometimes called DNA
fingerprinting. Gel electrophoresis can be used in DNA profiling.
Two major uses of DNA profiling are: Criminal investigations.
Paternity testing. The only major worry about the accuracy of DNA
profiling is the risk of contamination of samples.
Genetic Screening Genetic screening is the testing of an
individual for the presence or absence of a gene. This can be used
to test for certain diseases of which the gene responsible is
known. The question of whether genetic screening techniques should
be used in human populations has been widely discussed. There are
potential advantages but also possible disadvantages.
Advantages of Genetic Screening 1. Fewer children with genetic
diseases are born. Men or women who are carriers of an allele that
causes a genetic disease could avoid having children with the
disease by choosing a partner who has been screened and found not
to be a carrier of the same allele. 1. Frequency of alleles causing
genetic disease can be reduced. Couples who know that they are both
carriers of a recessive allele that causes a genetic disease could
use IVF to produce embryos screened for the allele. Embryos that do
not carry the allele could be used. 1. Genetic diseases can be
found and treated more effectively. If some genetic diseases are
diagnosed when a child is very young, treatments can be given which
prevent some or all of the symptoms of the disease. PKU is an
example of this.
Disadvantages of Genetic Screening 1. Frequency of abortion may
increase. If a genetic disease is diagnosed in a child before
birth, the parents may decide to have it aborted. Some people
believe that this is unethical. 1. Harmful psychological effects.
If a person discovers by genetic screening that they have a genetic
disease or will develop a disease when they are older, this
knowledge might cause the person to become depressed. 1. Creation
of a genetic underclass. People who are found to have a genetic
disease may be refused jobs, life insurance and health insurance
and be less likely to find a partner.
The Human Genome Project (HGC) Genome: the complete set of
genetic material of an organism. Humans have about 30,000-40,000
genes It is estimated that there are about 3.3billion nucleotides
in the human genome. The human genome project is an international
cooperative venture to sequence the complete human genome. Many
research groups around the world are working out the nucleotide
sequence of the different chromosomes, or parts of chromosomes. It
was started in 1990 and was originally estimated to take 15 years
but was finished in 2003.
The Human Genome Project (HGC) There are possible advantageous
outcomes from the HGC: It should lead to the understanding of many
genetic disorders. We will be able to easily identify genes that
cause genetic disorders and test people for them by making gene
probes. It will allow the production of new drugs based on DNA base
sequences of genes or the structure of proteins coded for by these
genes. Research into a particular disease can now focus on only the
gene (s) that are relevant to the disease. It can provide more
information about evolutionary paths by comparing similarities and
differences in genes between species.
Genetic Engineering Genetic material can be transferred between
species. This can occur because the genetic code is universal to
all living organisms. The process used to transfer genetic material
is called Genetic Engineering it is also known as Recombinant DNA
technology. For genetic engineering you need: The gene to be
transferred from the donor organism. Restriction enzymes
(restriction endonucleases). Ligase enzymes A host cell (usually a
bacterium) and their plasmids (circular rings of DNA.
Genetic Engineering Potential uses of genetic engineering fall
into three categories: To produce a protein product. Human growth
hormone. Endow a particular organism with a characteristic it did
not previously possess. Pest resistance in crops. To create more
copies of a gene. So it can be studied more.
Genetic Engineering The general steps in genetic engineering
are: Circular rings of DNA called plasmids are obtained from a
bacterium (E. Coli is commonly used). The plasmids are cut using a
particular restriction enzyme leaving sticky ends on the plasmid.
The same restriction enzymes are used to cut the required gene from
the donor organism, leaving the same sticky ends. The gene and
plasmids are combined and the gene is spliced into the plasmid
using ligase enzymes. The recombinant plasmid is reinserted into
the bacterium and allowed to multiply.
Ref: Biology, Campbell
Ref: Biology for the IB Diploma, Allott
Genetically Modified Organisms Organisms that have had genes
transferred to them are called Genetically Modified Organisms
(GMOs) or transgenic organisms. Some examples of GMOs are:
Herbicide resistance in crops. Sheep that produce human blood
clotting factor IX. Salt tolerance in plants. Delayed ripening in
tomatoes (Flavr-Savr). Bacteria use to produce insulin and clotting
factor VIII. Bt Corn resistant to insects.
Herbicide Resistance Herbicide resistance in crops: Almost all
plants are killed by the herbicide glyphosphate. A gene for
resistance to glyphosphate was discovered in a bacterium. This gene
has been transferred to maize and other crops. The transgeneic
crops can be sprayed with glyphosphate to kill the weeds but not
the crop.
Blood Clotting Factor IX in Sheep Sheep that produce human
blood clotting factor IX. A gene for the production of the human
blood clotting factor IX was inserted into sheep. They produce the
clotting factor in their milk, which can be collected and the
clotting factor extracted. The clotting factor can be administrated
to humans.
Gene Therapy Gene therapy is the treatment of genetic disorders
by altering the genome. Gene therapy involves the replacement of
defective genes with gene with the correct functioning alleles.
Examples of where gene therapy has been tried include: Treatment of
cystic fibrosis Treatment of SCID (severe combined immune
disorder). Treatment of thalassemia.
Benefits and harmful effects of Bt Corn Bt corn contains a gene
from Bacillus thuringiensis which produces a protein toxic to
specific insects( European corn borer). Benefits: 1. Damage caused
by insect reduced. 2. More expensive, but the difference is less
than one extra application of insecticide. 3. Non Bt corn needs to
be checked often for signs of the borer. 4. Less insecticide needed
means less impact on the environment. 5. Reduces the infection with
fungus also.
HARMFUL EFFECTS OF Bt CORN 1. Will also kill some other
insects. 2. Insects may develop resistance to Bt toxin because they
are exposed to it all the time. 3. Insects also make Bt spray
useless as insecticide( Bt spray is safe for humans and
environment) 4. It is difficult to prevent pollent (with Bt gene)
from travelling outside the field where Bt corn is grown. -it may
fertilise organically grown non Bt corn which can no longer be sold
as organic corn. - It may fertilise wild relatives and makethem
more resistant to insects and have them dominate the niche they
live in resulting in loss of biodiversity.
Cloning Clone is a group of genetically identical organisms or
a group of cells artificially derived from a single parent. The
technique for cloning using differentiated cells is mostly somatic
cell nuclear transfer but the use made of the produced cells can be
quite different like reproductive and therapeutic cloning.
REPRODUCTIVE CLONING Reproductive cloning creates a new
individual( Dolly was the first cloned sheep).Cloning using
differentiated cell. Steps involved in reproductive cloning 1. From
the original donor sheep to be cloned, a somatic cell (non-gamete
cell) from the udder was collected and cultured. Nucleus was
removed from the cultured cell. 2. An unfertilized egg was
collected from another sheep and its nucleus was removed. 3. Using
a zap of electric current, the egg cell and the nucleus from the
cultured somatic cell were fused together.
4.The new cell developed in vitro in a similar way to a zygote
and started to form an embryo. 5. The embryo was placed in a womb
of surrogate mother sheep. 6. The embryo developed normally. 7.
Dolly was born, and was presented to the world as a clone of the
original donor sheep.
Therapeutic cloning (cloning using undifferentiated cells) In
some cases, scientists are not interested in making an organism but
simply in making copies of cells. This is called therapeutic
cloning. In therapeutic cloning human embryos are produced, the
cells are referred to as embryonic stem cells Aim is to develop
cells which have not yet gone through the process of
differentiation. The cells can grow into any of a large number of
different specialised tissues. This cloning aims at cell therapy
where diseased cells are replaced with healthy cells.
Use of embryonic stem cells Growing skin to repair a serious
burn. Growing new heart muscle to repair an ailing heart. Growing
new kidney tissue to rebuild a failing kidney. Bone marrow
transplants for patients with leukemia.
Ethical Issues of therapeutic cloning in humans Arguments in
favour of therapeutic cloning 1. Ability to cure serious diseases
with cell therapy, currently leukemia and in the future possibly
cancer and diabetes. Arguments against therapeutic cloning 1.Fears
of it leading to reproductive cloning. 2. Use of embryonic stem
cells involves the creation and destruction of human embryos 3.
Embryonic stem cells are capable of many divisions and may turn
into tumours.
IBO guide: 4.4.1 Outline the use of polymerase chain reaction
(PCR) to copy and amplify minute quantities of DNA. Details of
methods are not required. 4.4.2 State that, in gel electrophoresis,
fragments of DNA move in an electric field and are separated
according to their size. 4.4.3 State that gel electrophoresis of
DNA is used in DNA profiling. 4.4.4 Describe the application of DNA
profiling to determine paternity and also in forensic
investigations.
IBO guide: 4.4.5 Analyse DNA profiles to draw conclusions about
paternity or forensic investigations. 4.4.6 Outline three outcomes
of the sequencing of the complete human genome. 4.4.7 State that,
when genes are transferred between species, the amino acid sequence
of polypeptides translated from them is unchanged because the
genetic code is universal.
IBO guide: 4.4.8 Outline a basic technique used for gene
transfer involving plasmids, a host cell (bacterium, yeast or other
cell), restriction enzymes (endonucleases) and DNA ligase. 4.4.9
State two examples of the current uses of genetically modified
crops or animals. 4.4.10 Discuss the potential benefits and
possible harmful effects of one example of genetic
modification.
IBO guide: 4.4.11 Define clone. Clone: a group of genetically
identical organisms or a group of cells derived from a single
parent cell. 4.4.12 Outline a technique for cloning using
differentiated animal cells. 4.4.13 Discuss the ethical issues of
therapeutic cloning in humans. Therapeutic cloning is the creation
of an embryo to supply embryonic stem cells for medical use.
