Chapter 13 Genetic Engineering

Selective Breeding Where did all the breeds of dogs come from? Humans bred dogs to have certain traits, breeding dogs that had the best versions Selective breeding only allows the traits we want to be passed down to the next generation Hybridization is crossing different organisms with two different desirable traits Disease resistance plant crossed with food- producing capacity plant

Dog Breeds

Selective Breeding Inbreeding is the continued breeding of organisms with similar characteristics Maintains desired characteristics Only allowing a dog to mate with another of its own breed Can increase the likelihood of genetic defect/disease

Increasing Variation Breeders can increase variation by inducing mutations, which are the ultimate source of genetic variability Mutations are inheritable changes in DNA Occur spontaneously or increase chance through chemicals and radiation Most are harmful, a few can be desirable Most useful in bacteria Used to create polyploidy (extra chromosomes) in plants, which is less harmful to plants

Manipulating DNA Genetic engineering is making changes in the DNA code of a living organism Remove the code Read the code Change the code Replace the code in the organism

Manipulating DNA Removing the code: extraction; DNA is separated from the other parts of the cell Extraction of DNA is done by rupturing the cells and adding a precipitating reagent such as ethanol, then DNA can be spooled onto a glass rod or sucked out with a pipette. Cutting DNA into pieces is done with restriction enzymes; each one cuts DNA at a specific sequence of nucleotides.

Manipulating DNA Separating DNA can be achieved by using gel electrophoresis The cut DNA is put into the well at one end (negative end – black) of the gel. DNA molecules are negatively charged and will travel to the positive end when current is applied Smaller fragments travel faster; separates DNA fragments based on size Used to create a genetic “fingerprint” or help isolate a gene

Gel Electrophoresis

Manipulating DNA Reading the DNA occurs by tagging some bases while copying the DNA, the colored tags help determine the order of bases Polymerase chain reaction makes copies of a particular gene

Cell transformation Transformation is the process of a cell taking outside DNA and incorporating it into its own Transgenic organisms are organisms with foreign DNA E.coli is used daily as a transgenic organism to produce human drugs, ex. human insulin and TPA (clot buster for heart attacks) Bacteria make great transgenic organisms because they have a tiny circular DNA, called a plasmid

Bacterial Transformation

Cell Transformation Foreign DNA is joined to the plasmid, plasmid DNA ensure that the sequence will be replicated Plasmid also has a label (genetic marker) so can distinguish if it has the gen Transforming plant cells involve using a bacteria that inserts a small DNA plasmid into the plant (normally causing tumors) Scientists inactivate the tumor gene, and use the bacteria to deliver the gene of interest

Transgenic Organisms Plants are important transgenic organisms. In the year 2000, 52% of soybeans, and 25% of corn grown in the US were transgenic (or genetically modified); most were modified for pesticide resistance Animals also being used, like the cow that makes milk with a human protein Modify mice to have immune systems to act like humans Animals the produce more growth hormone so they grow faster

Transgenic Cows http://www.livescience.com/14538-cows- humanized-milk-safe.html

Manipulating DNA Cloning – making a genetically identical organism from a single cell. In 1997, Ian Wilmut cloned, the now deceased, Dolly from the mammary cell of a sheep Gene therapy – using genes to treat diseases, such as cystic fibrosis Genetically modified organisms (food) – altered so less pesticides are needed

Dolly and Bonnie

Stem Cells Stem cells are unspecialized cells (not differentiated) All body cells have all the DNA, but only use the genes to make the proteins needed for that cell type once it becomes specialized Types: embryonic, amniotic, adult