Chapter 13 Genetic Engineering Selective Breeding Allowing only

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 �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.