Download Genetic engineering and biotechnology

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