Changing the Living World & Manipulating DNA Genetic Engineering Changing the Living World & Manipulating DNA

Selective Breeding Definition: breeding only those organisms with desired characteristics to pass on those characteristics to the next generation Hybridization: crossing dissimilar individuals to bring together the best of both organisms. Often hardier than the parents Inbreeding: the continued breeding of individuals with similar characteristics. Because of genetic similarities, the chance that a cross between two individuals will bring together two recessive alleles for a genetic defect is more likely.

Increasing Variation Breeders can increase the genetic variation in a population by inducing mutations. Mutation rate increases by using radiation and chemicals. Mutations are usually harmful to organisms, but sometimes a trait that breeders desire can be produced. Examples: bacteria that clean up oil spills, polyploidy (many sets of chromosomes) in plants

Manipulating DNa Scientists use their knowledge of the structure of DNA and its chemical properties to study and change DNA molecules. Different techniques are used to extract DNA from cells, to cut DNA into smaller pieces, to identify the sequence of bases in a DNA molecule and to make unlimited copies of DNA.

Manipulating DNa Genetic engineering: making changes in the DNA code by removing, reading, changing, and reinserting it into an organism. DNA extraction – cells are opened and DNA is separated from the other cell parts Cutting DNA – restriction enzymes are used to cut DNA into smaller pieces at specific nucleotide sequences Separating DNA – gel electrophoresis… a mixture of DNA fragments is placed in a porous gel, an electric voltage is applied to the gel, the negatively charged DNA molecules move toward the positive charge, the smaller the DNA fragment the faster it moves down the gel

Using the Dna sequence Once DNA is in a manageable form, its sequence can be read, studied, and changed. Genes can then be studied and compared. Reading the sequence Single strands of DNA are marked with a different fluorescent dye on each kind of base (A,T,G,C). The strand is terminated when the markers are added, resulting in different sizes of DNA that can be separated on a gel. Cutting and Pasting Synthetic sequences can be added to natural ones, producing recombinant DNA. Making Copies PCR (polymerase chain reaction) makes many copies of DNA by adding primers to a solution of DNA as well as DNA polymerase.