Chapter 13Genetic Engineering

Selective BreedingWhere 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 BreedingInbreeding 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 VariationBreeders 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 bacteriaUsed to create polyploidy (extra

chromosomes) in plants, which is less harmful to plants

Manipulating DNAGenetic 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 DNARemoving 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 DNASeparating 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 DNAReading 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 transformationTransformation 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 TransformationForeign 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 OrganismsPlants 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 Cowshttp://

www.livescience.com/14538-cows-humanized-milk-safe.html

Manipulating DNACloning – 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 CellsStem 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