Genetic engineering and biotechnology

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14 Δεκ 2012 (πριν από 4 χρόνια και 8 μήνες)

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Genetic engineering and
biotechnology

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
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.

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.

4.4.11 Define
clone
.

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


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
easily


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
correspond


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
individual


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

Applications of DNA profiling


Paternity


Match suspects


Studies of ecosystems


Social relationships


Migrating patterns


Nesting habits


Credibility to evolution

TOK


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


1990


2003



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
treatment

TOK


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?


http://www.blackgenocide.org/abortion.html


Why is abortion rates higher among
African
-
Americans?


http://www.blackgenocide.org/black.html



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
crops?

Cutting and pasting DNA


‘scissors’ made from enzymes


Restriction enzymes called
endonucleases

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
organism


DNA ligase

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


Copying DNA (DNA cloning)


Most of the genetic info for
E. coli

is in
the single chromosome


Some DNA is found in
plasmids


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

1.
Plasmid is removed from host cell and cut
using a restriction endonuclease

2.
Gene to be copied is placed inside the
open plasmid using DNA ligase (a.k.a.
gene splicing)

3.
Recombinant plasmid is used as a
vector

4.
Vector is placed inside host bacterium

5.
Bacterium allowed to grow and proliferate

6.
Bacterium expresses the gene and
synthesizes whatever protein the gene
codes for


Used to make human insulin


Genetically modified organisms
(GMOs)


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


Applications:


Delay ripening


Tolerate high salinity


Produce beta carotene


Could GM plants help solve world
hunger?

Transgenic animals


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


Examples:


Production of factor IX (protein needed
for blood clotting)


Resistance to parasites


Pre
-
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
needed


Production of rare proteins for
medications could be less costly


Greater control over crop or livestock
production


Lower need for water

Harmful effects, dangers, and
fears


Effect on ecosystems


Genes could cross species


Toxins to kill insects harmful to
humans


Allergies


Food supply property of small number
of corporations


May be simpler solutions


Decrease in biodiversity


Clones and cloning


Clone



group of genetically identical
organisms or a group of cells
artificially

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

1.
Somatic cell from donor sheep udder
was collected and cultured; nucleus
removed

2.
Unfertilized egg collected from
another sheep; nucleus removed

3.
Using a zap of electrical current, the
egg cell and the nucleus from the
cultured somatic cell were fused
together

4.
New cell developed in vitro and
started to form an embryo

5.
Embryo placed in the womb of a
surrogate mother sheep

6.
Embryo developed normally

7.
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
individual


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