Genetic engineering and biotechnology


14 déc. 2012 (il y a 8 années et 7 mois)

273 vue(s)

Genetic engineering and

Topic 4.4

Assessment statements

4.4.1 Outline the use of polymerase chain reaction (PCR) to copy and amplify
minute quantities of DNA.

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.

4.4.5 Analyse DNA profiles to draw conclusions about paternity or forensic

4.4.6 Outline three outcomes of the sequencing of the complete human

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.

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

4.4.10 Discuss the potential benefits and possible harmful effects of one
example of genetic modification.

4.4.11 Define

4.4.12 Outline a technique for cloning using differentiated animal cells.

4.4.13 Discuss the ethical issues of therapeutic cloning in humans.

Polymerase chain reaction (PCR)

Laboratory technique which takes a
very small quantity of DNA and copies
all the nucleic acids in it to make
millions of copies of the DNA

Way to ensure that enough DNA for
analysis can be generated

Gel electrophoresis

Laboratory technique used to separate fragments
of DNA in an effort to identify its origin

Enzymes used to chop up DNA strands into

Fragments are placed into small wells in the gel

Gel is exposed to an electric current

Heaviest, largest and least charged particles do
not move easily through the gel

Smallest, least massive and most charged
particles pass through the gel to the other side

Intermediate particles are distributed in between

In the end, the fragments leave a banded pattern
of DNA

DNA profiling

Process of matching an unknown sample of
DNA with a known sample to see if they

Referred to as DNA fingerprinting

If, after separation by gel electrophoresis,
the pattern of bands formed by two
samples of DNA fragments are identical, it
means that both came from the same

If the patterns are similar, it means that the
two individuals are most probably related

Applications of DNA profiling


Match suspects

Studies of ecosystems

Social relationships

Migrating patterns

Nesting habits

Credibility to evolution


How would you feel if you were to find
out from DNA profiling that your father
was not your biological father?

What effect would such a result have
on the relationships between siblings
or between spouses?

What kind of emotions might
someone feel after spending 18 years
in prison, and then being freed thanks
to a DNA test?

The Human Genome Project



Determined order of all the bases

Working now to decipher which
sequences represent which genes
and which genes do what

Can be useful in synthesizing
beneficial molecules as medical


What does the sentence, “We are all the
same; we are all different,” mean?

Can one genetic group be considered
genetically superior to another?

What has our history taught us?

Why is abortion rates higher among

Gene transfer

Technique of taking a gene out of one
organism (donor) and placing it in another
organism (host)

Ex. host tomatoes more resistant to cold
and frost due to donor DNA from a fish

Proteins used by fish to resist icy temp. of
arctic waters are now produced by the
modified tomato

Would strict vegetarians be able to eat a
tomato which has a fish gene in it?

What happens to local ecosystems which
rely on insects that may be killed by Bt

Cutting and pasting DNA

‘scissors’ made from enzymes

Restriction enzymes called

find and recognize a specific sequence of
base pairs along the DNA molecule

Sets of four or six pairs

Gene is cut out and released

Can then be removed from the donor

DNA ligase

pastes the genes to the sticky
ends in a particular portion of the DNA

Copying DNA (DNA cloning)

Most of the genetic info for
E. coli

is in
the single chromosome

Some DNA is found in

Plasmids are small circles of extra
copies of DNA floating around inside
the cells cytoplasm

To copy a gene, it must be glued into
a plasmid

Steps of copying DNA

Plasmid is removed from host cell and cut
using a restriction endonuclease

Gene to be copied is placed inside the
open plasmid using DNA ligase (a.k.a.
gene splicing)

Recombinant plasmid is used as a

Vector is placed inside host bacterium

Bacterium allowed to grow and proliferate

Bacterium expresses the gene and
synthesizes whatever protein the gene
codes for

Used to make human insulin

Genetically modified organisms

Organisms that has had an artificial
genetic change

Organisms produced to be more
competitive in food production

Transgenic plants

Undesirable gene removed

Desirable gene is put in its place

New gene is just added


Delay ripening

Tolerate high salinity

Produce beta carotene

Could GM plants help solve world

Transgenic animals

Used to produce a substance which
can be used in medical treatment


Production of factor IX (protein needed
for blood clotting)

Resistance to parasites

dyed wool

Show dogs

Faster racehorses

Benefits, promises, and hopes
for the future

GM crops will help farmers by
improving food production

Fewer chemical pesticides will be

Production of rare proteins for
medications could be less costly

Greater control over crop or livestock

Lower need for water

Harmful effects, dangers, and

Effect on ecosystems

Genes could cross species

Toxins to kill insects harmful to


Food supply property of small number
of corporations

May be simpler solutions

Decrease in biodiversity

Clones and cloning


group of genetically identical
organisms or a group of cells

derived from a single parent

Fertilized eggs do not differentiate until
after dividing many times

It was once thought that once
differentiated, the cell could not be used to
produce a clone

In 1996, a sheep named Dolly was born

First clone whose genetic material did not
originate from an egg cell

How Dolly was produced

Somatic cell from donor sheep udder
was collected and cultured; nucleus

Unfertilized egg collected from
another sheep; nucleus removed

Using a zap of electrical current, the
egg cell and the nucleus from the
cultured somatic cell were fused

New cell developed in vitro and
started to form an embryo

Embryo placed in the womb of a
surrogate mother sheep

Embryo developed normally

Dolly was born and presented as a
clone of the original donor sheep

Known as
reproductive cloning

Cloning using undifferentiated cells

Therapeutic cloning

involves the
copying of cells, not an entire

Aim is to develop cells which have not
yet gone through differentiation

Involves embryonic stem cells

Ethical issues surrounding
therapeutic cloning

Is it ethically acceptable to generate a
new human embryo for the sole
purpose of medical research?

Thanks to stem cell research may be
able to:

Grow skin to repair a serious burn

Grow new heart muscle

Grow new kidney tissue to rebuild a
failing kidney