Download Note 22

South Tuen Mun Government Secondary School
Biology Revision Note 22
Biotechnology – the use of biological knowledge (process and organism) to produce goods / services to man
Traditional biotechnology
Biological process and organisms involved
Selective breeding
Inheritance and selection – select crops / animals with desirable
character to breed
Making soya sauce
Fermentation – microorganisms e.g. fungi
Making bread, wine, beer
Alcoholic fermentation – microorganisms e.g. yeast
Making cheese, yoghurt
Lactic acid fermentation – microorganisms e.g. lactobacillus
Making compost / organic fertilizer
Decomposition – microorganisms e.g. fungi and bacteria
Modern biotechnology
 Genetic engineering – the use of recombinant DNA technology [please read note 20] to make desirable
genetically modified organisms (GMO) [recombinant DNA technology = manipulation of genetic
materials; to make GMO = change the genetic make-up of an organism, making it desirable for human
use]
The function of restriction enzyme – recognize specific base sequences and cut the double stranded DNA at
specific sites, producing sticky ends.
The function of ligase – join two adjacent pieces of DNA segments together
Vectors – is used to transfer a gene / DNA fragment from one organism (donor) to another organism (host).
e.g. plasmid – a small ring of double-stranded, extrachromosomal DNA found in bacteria [advantage: the base
sequence of many DNA plasmids is already known to biologists, thus it is easy to find cut site of restriction
enzymes; plasmid can be easily removed from bacteria and can be easily transferred to another bacteria;
plasmid can replicate on its own and it exists in many copies in one bacterial cell  many gene products from
the plasmid can be made]
e.g. viral DNA [advantage : the base sequence of many viral DNA is already known; it can infect a host cell e.g.
plant cell, animal cell or even human cell easily, thus its DNA is put into these cells, making these cells
transformed]
Applications of genetic engineering / recombinant DNA technology
An example of making a GM maize that is pest resistant
(i)
Making GM microorganisms e.g. bacteria / yeast to produce pharmaceutical products e.g. drugs (such as
insulin, human growth hormone), vaccines (hepatitis B vaccine), monoclonal antibodies (for diagnosis
of diseases, development of sensitive pregnancy tests, isolating and purifying important biological
molecules, treatment of some forms of cancers)
(ii) Making GM crops e.g. herbicide resistant, pest resistant maize; herbicide resistant, improved nutritional
value (good lipid) soya beans; pest resistant cotton; viral resistant papayas; salt tolerant, improved
nutritional value (higher level of beta-carotene that can make vitamin A = golden rice) rice; salt tolerant
wheat; salt tolerant tomatoes with a longer shelf life; improved nutritional value canola (good lipid)
(iii) Making GM animals e.g. fast-growing, cold resistant salmon; transgenic pig that produces more lean meat
and less phosphorus manure; transgenic goat that produces lactose-free milk or milk with less bad lipid,
with a higher quantity; transgenic cattle that produces milk with a higher quantity, transgenic sheep that
produces more wool, with a better quality
Benefits / advantages of genetic engineering:


In making drugs, a large amount of drugs can be produced rapidly, at a lower cost.
Probes (DNA fragments / monoclonal antibodies) can be made to diagnose diseases early / before birth.
[DNA probe contains single-stranded DNA with a base sequence that comes from a normal person, and is
labeled with radioactive isotopes. When it is added to a DNA sample from the foetus, if the foetus contain the
normal gene, it has a complementary base sequence that binds with the radioactive DNA probes, the DNA
sample becomes radioactive, thus he / she does not have the genetic disease. On the contrary, it the foetus
contain the abnormal gene, its DNA is not complementary to the DNA probe, it does not bind with the
radioactive DNA probes, thus the sample does not become radioactive, he / she has the genetic disease.]
 Food supplies can be increased by GM crops (herbicide resistant, pest resistant, disease resistance, cold
tolerant, salt tolerant, a longer shelf life) and animals (fast-growing, cold resistance, improved milk
production, improved wool production).
 The quality of food can be increased by GM crops (improved nutritive values e.g. more good lipid, with

special nutritive composition e.g. golden rice) and animals (improved lean meat with less fat; improved
milk composition; better wool quality)
Growing pest resistant GM crops reduces the use of chemical pesticide which is a chemical pollutant.
[Undesirable effect of chemical pollutant, such as killing non-target organisms and accumulation of
persistent toxic chemical pesticide along the food chain, can be avoided]

Transgenic pig, that produces faeces with a lower phosphorus content, can reduce the pollution caused by
manure.
Hazard / disadvantages of genetic engineering:
(i)


(ii)

Safety concerns / issues
In using GMO as food, the GM food may have long term, unknown health hazard.
GM food may be allergy to some people.
Environmental concerns / issue
If GMO leaks out to the natural environment, the antibiotic gene may be transferred to non target
organisms creating “super-organisms” e.g. superbugs, superweeds. The “super-organisms” / GMO itself
[sometimes the GMO itself is a “super-organisms”] may outcompete the wild type or they may have
unexpected dangerous effect to the wild type which will become extinct. The extinction of wild type may
upset the ecological balance [e.g. break the normal food chain, leading to extinction of other consumers
and reduce biodiversity].
Some other concerns of genetic engineering:
(iii) Ethical concerns / issues
 Are we playing the role of God who can create new GMO or interfere the nature?
 Is it ethical to make religious people (e.g. people who do not eat meat / animal products) intake animal
products because the GM plant has been genetically modified by an animal gene?
(iv) Social and economic concerns / issues
 GM products are highly technological, expensive products that are produced by rich, developed countries
(e.g. USA). As they are better in both in quantity and quality of products, most other countries would like
to buy these better products. Would this affect the income and the living standard of farmers in poor,
developing countries?

Polymerase chain reaction – replication / amplification of a very small amount of DNA (can be a gene),
so that a sufficient large amount of identical copies of DNA is produced by an instrument called thermal
cycler.
Step 1 : Denaturation of double
stranded DNA into single stranded
DNA at 95℃
Step 2 : Primers (synthetic short
length of single-stranded DNA that is
complementary to a short DNA
segment of the denatured DNA) are
added at 55℃. They bind at
complementary short DNA segment.
Step 3 : DNA polymerase and free
nucleotides (with nitrogen bases A, T,
G, C) are added at 70℃) [polymerase
is heat stable enzyme that will not be
denatured and is active at 70℃].
DNA polymerase catalyses the
binding of free nucleotides based on
the complementary relationship (A-T,
G-C) forming two identical copies of
double stranded DNA.
The thermal cycler repeats steps 1 – 3
of different temperatures for a
definite number of times. The number
of DNA copies = 2n where n is the
number of cycles.
PCR can be used
 to make a large amount of DNA probes that are used to diagnose genetic diseases and other diseases such
as SARS. When detecting diseases like SARS, it can also provide information of the mutations of the virus
and suggests whether the disease becomes more serious or not.
 in genetic engineering / recombinant DNA technology, to make a large amount of vectors (plasmid DNA /
viral DNA), so that the transfer of the vectors to the host cells can have a higher success rate.
 in DNA fingerprinting, the small amount of DNA in a small amount of blood, semen, saliva or hair can be
amplified so that it can be detected as bands.
 in human genome project, a small amount of DNA of a person can be amplified to make base sequencing
successful.

in plant and animal cloning [even very little amount of DNA in the cells of dead, extinct species found in
the past can be amplified, if it can be successfully cloned, the extinct species can become a living species
again.]
 DNA fingerprinting
In the 23 pairs of chromosomes of man, 95% of DNA do not code for functional proteins. They are known as
non-coding DNA. It is found that there are many alleles of variable number of tandem repeats (VNTRs) on
these DNA. The following diagram shows one allele of VNTRs.
homologous pair
of chromosomes
The VNTRs may be different in different people, but since a person receives his / her homologous chromosome
pairs from his / her parents, the VNTRs on one chromosome is the same as his father’s, while the other VNTRs
on the other chromosomes is the same as his / her mother’s.
The VNTRs are flanked by sequences that are conserved, that is, these flanking sequences are identical in
different persons. Thus they can be used as cut sites for restriction enzymes, so that the VNTRs can be cut.
Since the VNTRs are different in length and mass, they can be separated by gel electrophoresis.
The shorter / lighter DNA fragments move faster than the longer / heavier DNA fragments. A pattern of DNA –
DNA fingerprint is formed. This is because DNA fragments are negative charged, they move towards the
positive terminal under electricity.
The pattern of DNA is unique to an individual. It is thus very useful to identify an individual. Therefore, it can
used for victim identification in crime / rape cases. It can also be used in parentage testing. The more closely
related two persons are, it is more likely that some of their bands in the DNA fingerprint are the same.
Advantages of using DNA fingerprinting to identify an individual:
 DNA fingerprint is a highly accurate, reliable marker of the identity of a person / a species.
 Due to Polymerase Chain Reaction, a small amount of DNA can be amplified to produce sufficient DNA


for DNA fingerprinting.
Plant and animal cloning – the production of genetically identical copies of a plant and an animal e.g.
identical twins are clones.
The method of plant cloning is also known as tissue culture.
Cells from the carrot are isolated and
put into a sterile culture medium. The
cells change back into generalized
carrot cells that grow by mitotic cell
division to form into a callus.
The callus is cut into different groups
of cells. They are put into another
sterile culture medium. The cells
continue to grow by mitotic cell
division and differentiate into root,
stem and leaves, forming a plantlet.
The plantlets are put into a suitable
sterile culture medium and they
mature into an adult plant.
 There are two methods of animal cloning : embryo splitting and nuclear transfer.
Embryo splitting
Note : The clones are genetically
identical to each other, but they are
not the same as their parents.
Nuclear transfer
Note : the disadvantage of nuclear
transfer – the success rate is low;
the clone, Dolly, got older sooner
and had a shorter lifespan.
Application of cloning
 to clone endangered species [plant and animal]
 to provide stem cells for scientific researches [animal]

to generate genetically identical animals / plants (a desirable variety for higher productivity, nutritive value,
scientific interest e.g. for drug testing)
 to generate genetically modified animals / plants that can make drugs and other valuable chemicals
 to produce disease-free plants from plants that are infected (to preserve a variety of valuable crop / plant)
Advantages of plant / animal cloning:
 Cloning endangered species can preserve genes and reduce the chance of extinction.
 Cloning can save a variety that may have a difficulty to reproduce.
 Cloning genetically identical organisms and genetically modified organisms can increase the number of a
desirable variety for its higher productivity, nutritive value, scientific interest e.g. for drug testing. It can
clone genetically modified organisms to make drugs and other valuable chemicals.
Disadvantage of plant / animal cloning:
The clones have no genetical variation, they are less adaptable to a changing environment.
Ethical concerns of cloning
 The success rate of cloning is low. Some clones are dead. For example, in embryo splitting and human
reproductive cloning, many embryos are dead and destroyed. Is the death of these embryos justified?
 In human reproductive cloning, it is difficult to define the identity of the human clone. Is the human clone
an offspring of its single parent? Are the human clones from the same single parent brothers / sisters? If a
woman clones herself, is the woman or her clone the wife or daughter of her husband?
 Will the human clone be treated as a slave / a monster? Some scientist suggests that the human clone can
donate organs to a patient. Who should be the owner of the human clone? The doctor or the patient who
donates the cells for human cloning?
 Who should have the right to decide who can be cloned? Can rich people decide who to clone? Should
doctor decide the human cloning for organ donation? Should the intelligent / strong / healthy / beautiful or
handsome people be cloned to produce a “perfect” human race? Should superior historical people e.g.
Einstein be cloned so that he can re-lived?
 Is it possible that various valuable genes are engineered into a “perfect” human cell, so that a “perfect”
human race of identical individuals can be produced? Are we playing the role of “God” to design a
“perfect” or “superior” person?
Economic concerns of cloning
 The scientific study of cloning requires a lot of experimental testing. It is expensive. However, other
methods e.g. breeding, can be used to produce identical genetic individuals. Is it worth while to spend so
much money to clone an individual?
Environmental concerns of cloning
 In the cloning of endangered species, when the endangered species is released to the nature, it cannot
survive because it is becomes very unfit to live. Is it worth while to spend so much money to clone a
species that cannot survive in nature? Shall we spend more to conserve the environment so that the
endangered species can survive in nature?
[However, some scientists favour the human cloning because it can help people, who cannot reproduce, and
people who have their favourable son / daughter died accidentally, give identical son / daughter. As human
cloning is controversial, many countries ban the scientific research on human cloning.

Gene therapy – to supplement the diseased gene with a normal gene, so as to cure a genetic disease
In vivo gene therapy – the normal
gene enters diseased cells through
infection by virus. The virus is
genetically engineered to make it
harmless and carry the normal
gene.
In vitro gene therapy – diseased
cells are taken from the patient,
the normal gene is added into the
diseased cells to make them
genetically normal, these normal
cells are returned to the body.
Germ line gene therapy – correction is done through gametes / zygotes, thus all cells of the individuals are
normal and the correction can be inherited.
Somatic cell gene therapy – correction is done through the somatic cells that are defective, thus only some cells
of the organ are normal, the correction cannot be inherited.
An example: Severe Combined Immunodeficiency Disease (SCID)
Defective gene – fails to produce an enzyme in WBC  symptom : poor immunology response  death caused
by ordinary disease  patient can only survive in sterilized room to prevent infection
Treatment - adding the normal gene to WBC collected from the patient, returning the genetically modified
WBC into the blood of patient (in vitro, somatic cell gene therapy)
Result – the normal enzyme is produced by some WBC  better in immunological power of the patient  live
a normal life, outside the sterilized room
Disadvantage : the patient must receive the gene therapy frequently because the genetically modified WBC will
die naturally after a certain period of time, and is replaced by defective WBC made by the patient.
Further development of the method: the normal gene is added to the defective cells in bone marrow (the place
where WBC is made), genetically modified bone marrow cells can divide by mitotic cell division and produce
normal WBC, thus frequent gene therapy is not necessary.
However, these patients developed blood cancers later. We cannot say that the gene therapy is successful.
Potential benefits of gene therapy:
It brings hope to patients with genetic disease, to prevent genetic diseases that occur at an old age e.g. heart
disease, to prevent genetic disease that is known in foetus and to remove defective genes in the human
population.
Potential hazards of gene therapy:
 Viral vector may re-gain the ability of causing disease and cause unexpected immune response from the
patient. An unexpected severe immune response may cause death.



The adding of new genes to a cell may increase / decrease the expression of other normal genes 
unpredicted harmful effects
In in vivo gene therapy, the new genes may be added to non-target cells. Many unpredicted effects may
affect the normal functioning of the non-target cells.
Repeated gene therapy may increase the potential hazards of gene therapy to the patient.
Ethical concerns of gene therapy – it may be difficult to decide when gene therapy is allowed to be used.
 No one would disagree that gene therapy should be used to cure genetic disease. However should gene
therapy be used to cure genetic disabilities e.g. lower IQ, other personal-felt defects e.g. red eye, genetic
determined personality e.g. aggressiveness?
 Are scientists playing the role of God to develop gene therapy to change the genetic materials of the future
generation by germ line gene therapy? Will there be unpredicted harmful effect to the next generation?
Should scientists prevent the misuse of gene therapy to produce a perfect human race?
Legal concerns of gene therapy – by law, informed consent is important in medical choice: a patient should
have the right to understand the potential danger and benefits of a therapy because he / she makes a choice of
therapy. However, in germ line gene therapy, the person, that has its genes corrected, has not born yet. How can
scientist obtain informed consent from him / her? Is it illegal to change his / her genes before he / she is born?
Social concerns of gene therapy – would rich people be allowed to spend money on expensive gene therapy, so
that, they can be more and more “perfect” (more intelligent, prettier) and eventually the differences between the
rich and poor will be enlarged?
Economic issue of gene therapy
 Would rich people be able to spend a large sum of money in gene therapy, so they have a better chance of
survival as compared to people who cannot afford the cost of gene therapy?
 Should scientists look for other ways of curing genetic disease that are not expensive and can benefit both
the rich and poor, making a fair society?
 Stem cell therapy – stem cells are cultured to make different cell types / organs that are injected to replace
old / damaged cells of the same type / defected organs.
Stem cells are generalized cells that are capable to divide by mitotic cell division and to differentiate into other
cell types. Embryonic stem cells from blastocysts (4-5 days after fertilization) can be differentiated into almost
ALL types of cells. They are the best stem cells for therapy. As a person grows older, the ability of
differentiation by stem cell drops. Cord blood is less good than embryonic stem cell. Adult stem cells in bone
marrow, blood and skeletal muscles can only differentiate into a few cell types.
Stem cell therapy is a developing technology. It has a lot of problems:
 Taking the embryonic stem cells will damage the human embryo / blastocysts, will our offspring be killed?
 Sometimes the adult cells differentiated from embryonic stem cells are rejected / caused severe immune
response by the patients  unexpected health problem of patients.
 Adult stem cells are difficult to be isolated, difficult to culture and thus its number is very small. Moreover,
the number of cell types, the adult stem cells can differentiate into, is limited.
[Recent success: scientists successfully change human skin cells in generalized / unspecialized cells. These
unspecialized stem cell has the potential to differentiate into a wide range of cell types.]
Further development in stem cell therapy:
 To find out the culture medium / conditions to stimulate the differentiation of embryonic stem cells into a
desired cell type.
 When the differentiated cells are made from stem cells, for how long can they function after they are put
into the patient?

Are the unspecialized cells made from human skin cells safe to be used in stem cell therapy? Are there any
unpredicted, unexpected side effects?
Ethical concerns of stem cell therapy
 Is it a murder to destroy human embryo, to obtain embryonic stem cells?
 Do we have the right to destroy the life of an embryo, to save the life of a patient?
 Will the value of life be lowered if an embryo is made to be destroyed, to obtain the stem cell?
Legal concerns of stem cell therapy - can we be sure that the technique of stem cell therapy (where stem cell
collected from embryonic tissues is cloned) is not used in human reproductive cloning? Human reproductive
cloning is very controversial.
Social concerns of stem cell therapy – will the destruction of human embryo make the public lower their value
of life and become used to the destruction of human life?

Human Genome project
Human Genome Project
 To determine the base sequence of the DNA of a person. (DNA sequencing)
 To locate all the genes in the human genome. (gene mapping)
 To develop new technology / instrument for DNA sequencing and gene mapping.
 To discuss the ethical, legal and social concerns that are related with Human Genome Project.
Ethical concerns of Human Genome Project
After the base sequence of DNA and gene map are known to a person,
 When a person knows that he / she will develop a genetic disease that has no cure, what can he / she do?
Will it cause anxiety in their present life? What is the purpose that he / she knows about his / her genetic
disease?
 What happens when a person knows that he / she is superior / not as good as others genetically? How will
he / she feel?
Social concerns of Human Genome Project – if the genetic information is known to the public, how will the
people in the society see and feel about the person
Legal concerns of Human Genome Project
 Who owns the genetic information of a person? The person himself / herself; the company that does the
base sequencing and gene mapping; the government; the person who sends the cells for sequencing and
mapping?


Who can gain access to the personal genetic information? The person’s wife / husband; police; insurance
companies, employer?
How can we prevent discrimination and misuse of genetic information of a person? insurance companies,
school, employers?
 Can the presence of a “violence” gene be used as an evidence of a crime?
Economic concerns of Human Genome Project – is it worth to spend money to look at the genetic information
of a person, to find out genetic defects or genetic superiority? Shall we put the money in other areas e.g. healthy
lifestyle, to promote our life?
The concept of bioethics:
 Any ethical / moral, social, economic, legal issues / concerns related to modern biotechnology and
medicine
 Many of the issues / concerns are controversial. There is no definite “right” or “wrong”; it depends on
“value” of a person, some people may think that the technology is beneficial and some do not!