- Artificial selection methods: selection
of desired traits in plants and animals by man
('Artificial' selection as opposed to 'natural' selection:
we have and are further developing the ability to manipulate genetic information
into generating (in plants and animals) traits that we desire. The difference
between 'natural' selection and 'artificial' selection is the source of
the selective pressures: in the former, it is 'nature,' while in the latter,
it is humankind.) Using genetic engineering, people have developed more
productive
- Breeding programs: breeding of
selected plants and animals to produce descendants with desired characteristics
Example: by controlling the breeding of the most
milk-productive dairy cows, we can produce offspring that are as, if not
more, milk-productive.
- Cell culture: growing cells outside
a living organism
(self-explanatory)
- Advantages over breeding programs:
- Permits study of identical cells
This is important in identifying and studying specific
traits, and with greater precision than is possible with breeding programs.
- Rapid identification of desired
trait
Breeding is much more time-consuming and difficult
to deal with.
- Human cancer cells in cultured
medium
Example: one of the most famous cancer-cell lines
we have is from Henrietta Lack, who died of cervical cancer. Scientists
have cultured them to study in procuring treatments, etc..
- Plants: cells ==> callus ==>
plantlet
A callus is a group of undifferentiated cells; just
cells going through mitosis--not a part of an organism. The callus can
be treated with chemicals, (different concentrations of sugar, for example),
which will cause differentiation: roots grow from some cells, stems and
leaves from others, generating a plantlet (organism).
- Recombinant DNA: combining segments
of DNA from different sources to form "recombined" DNA
(The initial experimentation with recombinant DNA
took place in 1973.)
- Recombinant DNA technology
 20.1
Recombinant DNA Technology
(Scientific breakthroughs often result from research that is not specifically
addressed to solve a problem, but is initially done for the sake of experimentation
alone. Such is the case with recombinant DNA technology.)
- The process of recombining DNA:
(example: human insulin)
Until relatively recently, diabetics would often
use bovine (cow) insulin, as human insulin wasn't readily available. But
with recombinant DNA technology, such is no longer the case.
- Locate desired gene on donor chromosome
(the human gene that regulates insulin production)
Before we can engineer with genes, we must identify
what genes do. In this case, the gene responsible for the production of
insulin has been indentified. (This technology demonstrates the value of
the Human Genome Project.)
- Remove bacterial plasmid ( 20.2
Plasmid DNA Vector)
DNA from donor bacteria
- Using a restriction enzyme ( 20.3
Restriction Enzymes)
"cut"
Restriction enzymes (DNA scissors) 'cut' the DNA
at specific locations, leaving the DNA in pieces with 'sticky ends,' as
shown in the diagram.
- gene from human chromosome
- plasmid DNA
- Using ligase enzymes, (20.4
Ligase Enzymes) splice donor gene into plasmid DNA
Ligase enzymes (DNA glue) assist in the piecing together
of the DNA fragments at their 'sticky ends'.
- Insert plasmid with recombined
DNA back into plasmid DNA
The plasmid is moved in and out of the cell easily,
by 'heat-shocking.'
- Clone the bacteria
The bacteria with the recombined DNA is mass-produced
in order to provide the necessary amount of product.
- Filter and purify the product:
(human insulin)
The insulin produced by the recombined bacteria is
made available to diabetics.
- Vectors used in recombinant DNA
technology
(A vector is a carrier.)
1. Bacterial plasmid DNA
2. Viruses / retroviruses
3. Mammalian cells (i.e. mice cells)
4. Fungus (yeast)
5. Phosphorous (the element): an inorganic vector
- Applications of genetic engineering
- Human systems
- Insulin
- Retrovirus: "Bubble children"
20.5
Genetically Engineered ADA
- Plant systems
- Crown gall vector: Agrobacterium
tumefaciens
- Issues concerning genetic engineering
- Environmental issues: the release
of genetically engineered organisms
- Social issues: economic issue in
agriculture: transgenic animals
- Ethical issues: reconstruction
of human genome
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