Transcript Chapter 13
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 foodproducing 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-cowshumanized-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