Genetics 2 Flashcards
DNA PROFILING
The term DNA fingerprinting or DNA profiling is used to show the special pattern some fragments of DNA have. Humans and other organisms have short tandem repeats which are sequences of bases that are repeated many times, called satellite DNA. This satellite DNA varies greatly between different individuals in the number of repeating units (i.e. CACA – two bases repeated two times). It is unique to every one of us like our fingerprint. Usually between 11 and 13 of STR loci are commonly used in DNA profiling methods. It is highly unlikely two people to have the same profile unless they are identical twins.
This phenomenon of natural variation is a tool used for different purposes such as :
• Forensic investigations and solving criminal cases
• In paternity and pedigree disputes
• In disease screening (searching for a specific gene)
• In identifying the identity of a dead (Egyptian mummies)
GENE SEQUENCING
DNA sequencing is the process of determining the precise order of nucleotides within a DNA molecule. It includes any method or technology that is used to determine the order of the four bases—adenine, guanine, cytosine, and thymine—in a strand of DNA.
GENETIC MODIFICATION
One gene, coding for a given desirable characteristic, is carried (transferred) into another organism not naturally possessing this characteristic. The organism which obtains the foreign gene becomes a GENETICALLY MODIFIED ORGANISM or GMO.
Genetic material can be transferred between species because the genetic code is universal and therefore desirable qualities can be given to foreign species.
By this method pharmaceutical products can be produced such as INSULIN. Insulin is a small protein made of 51 amino acids. It is needed to treat diabetes.
Several structures and chemicals and needed during the procedure.
Plasmids: Small circular pieces of DNA found in bacteria. They contain a few genes- especially genes for resistance to antibiotics.
A host cell: Either a bacterium (studies of E. coli are well documented) or a yeast cell (eukaryotic).
Restriction enzymes (Endonucleases): Special enzymes the cleave (cut) the DNA at specific base sequences
DNA ligase: Enzyme that splices (rejoins) pieces of DNA -in the case of a plasmid it closes the plasmid again.
With this method CLONES of bacteria are finally produced. Clones are a group of genetically identical offspring which are produced by asexual reproduction.
Method
A plasmid is extracted by a bacteria cell
• The mRNA molecule is extracted from Target cells (ie. Human pancreatic
cells) which secrete insulin
• From mRNA dsDNA is synthesized called cDNA
• Both the plasmid and the cDNA are treated with the SAME RESTRICTION ENDONUCLEASE
• The plasmid is cut open and sticky ends are produced. The same sticky ends are present in the cDNA
• Both the open plasmid and the treated cDNA are mixed together with DNA LIGASE
• A recombinant plasmid is produced which is then added into a host cell (i.e. bacterium E. coli)
• Bacteria left in culture medium start to synthesise insulin which is then extracted, purified and given to the market
Benefits and risks of genetic modification
Benefits
Less pest damage-therefore higher crop yields to help reduce food shortages
Less use of insecticide sprays which are expensive and harmful to workers and wildlife
allows crops to be grown where they would not grow naturally, since varieties resistant to cold, drought or salinity can be produced
provides more food, with higher nutritional value, for example increasing the content of a certain vitamin
lowers cost of production
reduces the need to clear rainforests to grow crops
Harmful effects
Eating the bacterial DNA might be harmful for health, such as appearance of allergies
Other insects-not pests- could be killed eating nectar from flowers of GMO plants
May affect food chains or have unintended effects on other organisms Long-term effects are unknown
Populations of wild plants might be changed. Cross-pollination might affect wild plant populations- obtaining the Bt toxin might have a selective advantage over others
Risk of long-term contamination of soil
CLONING
A clone is a group of genetically identical organisms or a group of genetically identical cells derived from a single parent. Cloning is a form of asexual reproduction. Most plants can be easily cloned from pieces of root, stem or leaf. Cloning in animals and humans happens naturally-monozygotic twins.
Cloning in animals is necessary if these animals are carrying genetic information for production of pharmaceutical biochemicals. These animals are called transgenic animals and they have in their genome one or more foreign genes which will produce pharmaceutical products of great importance. In order for these animals to multiply we are using clones (identical multiples). In early divisions a fertilised egg produces 8 cells each of which could give rise to an embryo. After in vitro processes the 8 resultant separated embryos can be transferred to surrogate mothers (e.g., cattle of sheep) to continue growth of the embryos and finally give birth to them which in turn will either be used to select the desired product ( e.g. from their milk) or to select new gametes.
The first successful cloning of an adult with known characteristics produced Dolly the sheep.
