Chapter 13 Genetic Engineering Changing the Living World
Selective Breeding Humans use selective breeding, which takes advantage of naturally occurring genetic variations. Domestic animals Farm animals Crop plants Pass desired traits to the next generation
Hybredization Luther Burbank may have been the greatest selective breeder of all time (1849 – 1926) Used Hybredization crossing dissimilar individuals to bring out the best in each Combined the disease resistance of one plant with the food-producing capacity of another The result was a new line of plants that allowed farmers to increase food production
Inbreeding The continued breeding of individuals with similar characteristics Breeds of dogs such as beagles and poodles Risks Chance that two recessive alleles form a genetic defect Joint problems with German shepherds for example
Increasing Variation Selective breeding is possible because of the wide variation found in natural populations Breeders increase the variation by inducing mutations (mutations are the cause of variations) With luck over a number of attempts desirable traits may be found.
Increasing Variation 2 Because of the small size of bacteria, radiation or chemical treatment may produce some of the bacteria with useful characteristics. Bacteria that digest oil Bacteria that produce hydrogen
Increasing Variation 3 Producing new kinds of plants Prevent chromosomal separation Sometimes produce cells that have two to three times the number of chromosomes Called polyploidy the extra chromosomes in plants sometimes make them larger and stronger. Polyploidy is fatal in animals
Manipulating DNA Scientists have broken the DNA code They study the structure of DNA and its chemical properties. Techniques are used to extract DNA from cells and cut it into smaller pieces and identify the sequence of bases in a DNA molecule and make unlimited copies.
Manipulating DNA Tools DNA extraction – chemicals can separate the DNA from other cell parts. Cutting DNA – Restriction enzymes are known and each one cuts DNA at a specific sequence of nucleotides.
DNA fragments can be separated using gel electrophoresis DNA fragments can be separated using gel electrophoresis. A DNA fragment is placed at one end of a porous gel, and voltage applied. DNA molecules, which are negatively charged move to the positive end of he gel. The sequence can then be read.
Applications of Genetic Engineering Transgenic Organisms – It is possible to construct organisms that are transgenic, meaning that they contain genes from other species. The transformed cells grow new organisms. Transgenic microorganisms – transgenic bacteria now produce substances that form proteins cheaply and in great quantities. ie. Insulin, growth hormone, and clotting factor
Cloning A clone is a member of a population of genetically identical cells produced from a single cell.