Chapter 13 Genetic Engineering

Selective Breeding Allowing only the animals with desired characteristics to produce the next generation Cats, dogs Horses, cows Potatoes,tomatoes

Hybridization Crossing dissimilar individuals to bring together the best of both organisms Luther Burbank (Botanist from Santa Rosa) Disease resistant potato

Inbreeding Continued breeding of individuals with similar characteristics Dogs Sometimes the cross brings together two recessive alleles for undesirable characteristics-joint deformities in German Shepherds and Golden Retrievers

Increasing variation Breeders can increase the amount of variation by inducing mutations. Some will cause desirable characteristics. They then selecting individuals that carry the mutation and breed them Uses chemical or radiation to induce mutations Most useful with bacteria and plants Bacteria that can digest oil Polyploid plants (many sets of chromosomes) Makes the flowers and the fruit bigger and better looking

Manipulating DNA-Molecular Biology Genetic engineering-making changes in the DNA code DNA extraction-remove the nuclei from the rest of the cell Density gradient centrifugation Use detergent to dissolve the nuclear membrane, isolate DNA

Manipulating DNA-Molecular Biology Genetic engineering (cont) Cutting DNA-too big to be analyzed, so cut the DNA into smaller pieces with restriction enzymes, each specific to a certain sequence of DNA Separating DNA-The cut up pieces (restriction fragments) can be separated according to size by gel electrophoresis . A current is passed through a gel that contains the DNA(like a molecular strainer, separates by size, small pieces travel faster)

Using the DNA sequence After cutting and separating the DNA, the sequence can be read, and the sequence can be changed To read the sequence: The DNA is copied In the copies, the A’s, T’s C’ and G’s at the end of each piece are tagged with different colored fluorescent dyes Each copy is only partial, and each one is a little longer than all the others The pieces are separated by length, and the detector then detects the different colors at the end of the sequences, and puts it all together like a nested puzzle to give the sequence

Using the DNA sequence Recombinant DNA Takes a gene from one organism and puts it in another organism; e.g. human gene for insulin put into bacteria to make insulin for individuals with diabetes

Using the DNA sequence Copying the DNA-PCR Polymerase chain reaction A reaction that replicates short strands of DNA Can make millions of copes from a single molecule uses a form of DNA polymerase that is active at high temps The form of DNA polymerase was discovered in the hot springs of Yellowstone (“Taq”, for Themophilis aquaticus) Invented by Kary Mullis, a professor at UCSC, and a surfer. Said he got the idea for the reaction while surfing

Cell transformation A cell takes in DNA from the outside and the DNA becomes a part of that cell’s DNA Bacteria, plant and animal cells

Cell transformation In Bacteria, the introduced DNA joins into a DNA molecule in the bacteria called a plasmid Plasmids occur naturally in bacteria Plasmids often carry drug resistance genes Plasmids have an origin of replication and a genetic marker, to allow it to be distinguished from other bacteria often a drug resistance marker the bacteria are grown in the presence of the antibiotic the cells that don’t have the plasmid die, so it is a way of selecting The gene encoded on the foreign DNA is expressed as protein in the transformed cell

Applications of Genetic Engineering Transgenic organisms Bacteria that produce insulin Animal models to study human diseases and treatments for them Plants that are resistant to weed killers

Cell transformation Plant Cells A plasmid is used that causes tumors in plants The transformed calls integrate the foreign DNA into their own chromosomes The gene encoded on the foreign DNA is expressed as protein in the transformed cell

Cell transformation Animal Cells Can inject eggs with DNA Other ways to trick the cells into taking up DNA DNA may or may not integrate into cellular DNA The gene encoded on the foreign DNA is expressed as protein in the transformed cell

Applications of Genetic Engineering Cloning Clone is a member of a population of genetically identical cells produced from a single cell Sheep “Dolly” An nucleus of an egg was fused with a cell taken from another adult. The embryo is placed in the uterus of another adult sheep. The offspring, “Dolly”, was genetically identical to the original adult cell.