chapter 13
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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 - PowerPoint PPT PresentationTRANSCRIPT
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