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Biotechnology and its applications p. 158
Human Genome Project – The identification of the human genome, that is, finding out all
the base sequences. Mapping of genes – what the sequence codes for. (did mapping of
genome of yeast in 1992 just for chromosome 3 which consisted of 315 357 nucleotides,
took about 10 years.)
Thought that DNA → RNA → proteins → control the body, based on that and looking at
all the different phenotypes, figured we must have a lot of genes, 100, 000’s. Only about
25, 000. (doesn’t seem to be enough to account for all the different varieties) And found
that most of the genome is not transcribed into genes – called it ‘junk DNA’. Most of
this junk consisted of highly repetitive sequences of DNA up to 3000 base pairs long.
Makes up 5-48% of genome and now think these highly repetitive sequences (satellite
DNA) may help determine how genes are expressed. As opposed to unique or singlecopy genes.
Half of the genes had an unknown function. Need to know three.
Pros – health care in identification of diseases and find location NOT the cure;
new probes for diseases
Insight into how the body works; production of new drugs
Evolutionary information – relationships
Produce better drugs based on DNA: better understanding of genetic diseases
Cons – money spent
What can it be used for – expand.
Who will be allowed access to information?
PCR – Need more, see textbook. Polymerase chain reaction – is a method for making
many copies of a specific segment of DNA. It is performed in vitro. In many
biotechnologies, a great deal of DNA is needed. In crime scenes or fossil remains,
usually only a drop of semen or blood is found. More is needed so this technique
supplies many copies of the DNA sample.
Gel Electrophoresis – separates macromolecules like DNA, on the bases of their
movement through a gel under the influence of an electric charge. Mixtures of DNA
fragments of different sizes are added to the gel at the –ve end or cathode. When the
electricity is turned on, the fragments will migrate to the +ve end (anode) at a rate
DETERMINED BY THE FRAGMENTS CHARGE AND SIZE. The shorter fragments
of DNA will travel farther from the –ve end. What you end up with is a gel with bands of
DNA. If the gel is treated with a dye, the bands can easily be seen and analyzed. See
diagrams.
DNA profiling (DNA fingerprinting) – blood, semen or other body samples are taken.
Amplified with PCR. It is cut with restriction enzymes to cut it into fragments. Then gel
electrophoresis is done. The bands we use to note differences are our junk or
repeating sequences of no apparent use. The sequences of DNA used to code for
organs etc should all be the same for every person. It is just our junk that is unique.
And that is what is used for our DNA fingerprint. Need two uses and the constant
problem of contamination. Used for paternity suits, forensics
Recombinant DNA- (gene transfer) the techniques used to transplant genes from one
living source into another where it will be expressed. See diagram. Know restriction
enzymes, ligase, vector
Gene Therapy – faulty gene is replaced by a good gene. Only works if faulty gene is
recessive; only works on diseases cause by one gene; get good gene, need restriction
enzyme; make copies; PCR; introduce into another organism like a virus; need restriction
enzyme and ligase; virus infects person and inserts its DNA into our cells. Tried for
cystic fibrous. Results only temporary.
Genetic Modification (Engineering) – you find out. Crops improved by it; cauliflower,
asparagus, corn, cucumber, cotton, eggplant, grape, raspberry, lettuce, papaya, pea,
pepper, plum, potato, tobacco, rice, strawberry, sugar cane, tomato, walnut, wheat. Cons
– genes cross species barrier, affect other genes, take over other genes to become
dominant
need to give named example like herbicide resistance
Pros – more specific breeding; faster than traditional
Increased food production; less chemicals used
Less use of drugs; less expensive
Cons – could be potential harm to other animals
Could be released into the environment
Could spread without competition; cross species barrier
Reduce genetic diversity
*Eg. Wheat genetically modified
DNA (gene) source is Salmonella Typhimurium
Effect – resistance to roundup herbicide
Benefit – allows use of herbicide on growing crop, control weed but doesn’t affect crop
Yields are higher
Harmful effect – gene may be transmitted to weeds
Uncontrollable crop/superweed
Or foreign DNA may have affect on humans like allergies
Cloning – know procedure.
Genetic screening – know – of embryos in IVF, will take in genetics pros – prevent births
of affected children, eliminate genetic diseases from population, reduce stress on parents
Cons- allows selection of embryos, euthanizing of embryos with disease
Gene transfer – using reverse transcriptase, plasmids cut with endonucleases, addition of
“sticky ends” to DNA, copy, combine into DNA with ligase → recombinant plasmid,
used for insulin production
* Go back to Stem cells – 2.1.8 do now!!
Genetically modified questions used a lot