Chapter 13

 Breeding organisms for specific characteristics  Ex: Pedigree Dogs, livestock, horses, plants  Two Types of Selective Breeding: 1) Hybridization – combines traits from two different organisms of the same species 2) Inbreeding – maintains desired traits within a population of a species

 The offspring from hybridization are most often healthier than either parent  Increases genetic variation in a population  Reduces the risk of an offspring inheriting a genetic disorder  Example: Mutt dogs, Labradoodles, Maltipoos, Burbank Potato  Burbank Potato:  Created circa 1900’s by Luther Burbank  End to Ireland’s Potato Famine  Resistant to mold/disease, increased food production

 Once a desired characteristic is created in a population, inbreeding allows that characteristic to be maintained over generations  Only happens inside a specific population of organisms  Increases chance of an offspring inheriting a genetic disorder  Limits variation in a species  EX: Purebred pedigree dogs: Golden Retrievers, Poodles

 Breeders can increase genetic variation in a population by inducing mutations which are the ultimate sources of variability  A mutation is ANY change in DNA  Factors that cause mutations are called Mutagens  Ex: Chemicals, Radiation (such as UV radiation)  NOT ALL MUTATIONS ARE BAD!  Mutations that somehow benefit the organism and increase the organisms chance of reproducing in the wild or captivity may lead to evolution

 Other than using selective breeding, scientists may directly change and play with DNA for Genetic Engineering  Basic idea: Remove the DNA from a few cells, edit and change the DNA using test tubes and lab chemicals, replace the altered DNA into new cells and possibly place the new cells with altered DNA into an organism

 A variety of laboratory techniques and tools are involved  Restriction Enzymes: Enzymes that cut DNA at specific nucleotide sequences  Gel Electrophoresis: organizes DNA fragments according to size  Recombinant DNA: Creating DNA molecules (plasmids) with portions from more than one organism  Polymerase Chain Reaction (PCR): Creating multiple copies of a short segment of DNA in a test tube

 Restriction enzymes are enzymes that are naturally found  They ‘recognize’ specific nucleotide sequences of DNA and cut the DNA in a specific location  EX: The restriction enzyme EcoR I cuts DNA in the middle of the TTAA sequence  Scientists may use these enzymes to chop up DNA fragments so they may isolate specific genes  These genes may later be combine with DNA from another source (such as bacteria), creating Recombinant DNA

 This process organizes DNA according to size  Allows scientists to study and mutate specific sizes and sequences of DNA  The gel itself is about the size of a small paperback book, looks like clear jell-o and is about ¼ inches thick  There are different gels for different purposes  Procedure  Put tiny DNA fragments in a small test tube  Dye the DNA blue  Inject the DNA into the “wells” with a pipette (a scientific eye-dropper)

 Place gel in plastic box and hook up “jumper cables”  Pass electric current through gel  DNA moves (-) to (+) because DNA is (-) charged molecule  Small pieces move farthest the fastest  This process may be modified and used to “read” DNA sequences too!

 Once a desired sequence of DNA has been isolated and replicated (via PCR), it may be fused into a plasmid in a bacteria  A plasmid is a short circular piece of DNA naturally found in bacteria  Bacteria cells containing recombinant DNA plasmids will produce the proteins coded for by the Recombinant DNA  EX: Bacteria that produce Human Insulin for diabetics

 Once a desired segment of DNA is isolated (via gel electrophoresis), the DNA may be replicated to produce hundreds of thousands of copies  These copies may be inserted into bacteria plasmids to create recombinant DNA bacteria  PCR uses cycles of heating and cooling in a test tube and the DNA polymerase of a special bacteria to produce lots of copies

 When recombinant DNA plasmids are inserted into living bacteria cells, the process is called transformation  These transformed bacteria cells can produce the proteins in the plasmids and they reproduce very rapidly  Allows scientists to mass produce proteins to medical use  Ex: Human insulin and Human Growth Hormone  Genetic Markers allow scientists to locate cells in a colony that contain the desired plasmids  Genetic markers are genes that make the bacteria resistant to specific antibiotics.  If a colony of bacteria are treated with the specific antibiotic, only the ones that survive contain the desired plasmid  Bacteria transform pretty easily, plants cells is more difficult, animal cells even more so, however, inserting recombinant DNA into animal cells (such as human brain cells) is difficult. This is the basic idea behind current Gene Therapy research

 Transgenic Organisms – organisms that contain genes from other species  Examples:  Jellyfish Pig – See handout  Livestock with extra Growth hormone genes,  Bacteria that Produce hormones such as insulin and Growth Hormone  Transgenic plants make up about 50% of our food industry  Cloning – clones are members of a population of genetically identical cells produced from a single cell  Bacteria colonies produced from a single cell are all clones  Multicellular animals have been cloned: Dolly the sheep, Copy Cat etc.

 A nucleus from the body cell of a donor organism (the animal being cloned) is implanted into an egg cell which has no nucleus (removed by the scientist)  Once the egg cell “senses” a complete set of chromosomes in its nucleus, it begins to divide and reproduce like any other fertilized egg  This egg is then implanted into a Foster mother’s uterus where it grows and develops into a normal baby  Interesting side note: Clones DO NOT live as long as the organism they were cloned from….has to do with being made from “old” DNA