Genetic Engineering

Selective Breeding People have been practicing gene manipulation for hundreds of years One way we have been practicing genetic engineering is through a process called selective breeding. Selective breeding occurs when we choose animals with favorable traits and breed those animals and do not breed animals with traits we find unfavorable.

Selective Breeding Selective breeding is regulated by two principles” Hybridization – crossing two organisms that are not similar to hopefully get the best of both organisms Inbreeding – breeding very similar animals to preserve the traits the are present in that line of organisms. This can cause recessive alleles present in these lines to show up causing unnecessary illness.

Increasing Variation Sometimes we want new varieties of an organism, so we induce mutation. Mutations are the main source of genetic variation, it’s how new traits form Breeders can use radiation and chemicals to force mutations to occur. Most of the time these mutations are harmful to the organism, but occasionally a favorable mutation will appear. This is an ethical issue with animals, so we only practice these methods with bacteria and plants

Genetic Engineering Genetic engineering is making changes in the DNA code of a living organism We already know that we have read certain organisms DNA sequence, and that we can analyze it using gel electrophoresis, but we can also transform DNA using recombinant DNA and viruses

Recombinant DNA Restriction enzymes are proteins that cut DNA at specific sites. For example BamI cuts DNA wherever it sees at CTAG sequence. So, where would BamI cut this strand of DNA? G T C T A G C G T A C A C T G C T A G A A C G T C A G A T C G C A T G T G A C G A T C T T G C A

Recombinant DNA Synthetic DNA can be made in a lab using a machine called a DNA synthesizer. The scientists can join natural pieces of DNA to synthesized one using enzymes that splice DNA back together They can also combine DNA from two completely different organisms together This is called recombinant DNA because it combines the DNA from two different sources together

Polymerase Chain Reaction This is a process that allows us to make many copies of a strand of DNA very quickly The first step is to denature the DNA or separate the two strands This is done by heating the DNA up to about 94-96oC Then we lower the temperature and add primers that will attach to specific sequences in the DNA The polymerase attaches to the DNA strand and replicates a complimentary strand of DNA

Polymerase Chain Reaction This process is repeated continually creating copies of copies of copies and increasing the amount of DNA exponentially This process allows researchers to make many copies of unique segments of DNA and store them or share them That way if we find a tiny sample of DNA at a crime scene we can replicate it to make as much as we want to test many times

We’ve made the DNA we want, copied it, but now how do I get it into an organism?

Transformation Transformation – when a cell takes DNA from outside the cell and integrates it into the cell’s own DNA This can be done three ways Natural uptake of DNA from surroundings Injection with a needle Using a virus to inject the DNA

Some bacteria are able to naturally able to pick up DNA and sometimes humans control it Scientists create a piece of DNA called a plasmid These plasmids need to have a origin for replication and two ends that a specific restriction enzyme will cut Wherever it cuts the bacterial DNA is where the plasmid is inserted Sometimes these changes add a gene that make a bacterial cell resistant to antibiotics Bacteria

Animal Cells DNA can be inserted into larger cells such as egg cells with a needle We also use viruses to inject DNA into cells A virus naturally injects its own DNA into other cells, so if we replace the harmful virus DNA with a favorable gene the virus will inject that gene into the cell.

Sometimes we just randomly insert needed recombinant genes into the DNA, but sometimes we target specific areas for insertion We can target specific genes that are unfavorable and insert the recombinant genes in its place so it “knocks out” that gene Animal Cells Recombinant DNA Host Cell DNA Target Gene Modified Host Cell DNA

Why Engineer It allows us to create transgenic organisms that help support our population Pest resistant crops Crops with added nutrients that taste better Cows who produce more growth hormone Plants or bacteria that will produce plastics We can use small, quickly reproducing organisms to generate medicine cheaply Bacteria can contain genes to make insulin or human growth hormone Some microorganisms were developed to digest oil We can insert some of our DNA into animals to study the affects of disease

Stem cells are cells that have not yet differentiated and can become any type of cell still There are adult stem cells, and embryonic stem cells, but adult stem cells can only produce one type of cell So, it is more beneficial to use embryonic stem cells for research, but it requires destroying an embryo. Stem Cells Stem cells could possibly be used to produce any other type of cell or structure, they could be used to cure diseases

Cloning In 1997 we successfully cloned our first mammal, a sheep named Dolly They took a cell from one sheep and an egg cell from another. They removed the nucleus from the egg cell and then fused it with the other cell using an electric shock. They then implanted this egg cell into the uterus of a foster mother who gave birth to Dolly

Current Work in Genetics

Ethics What do you think about genetic engineering, stem cells, and cloning? Is it right or wrong?