Genetic Engineering How it all begins Sexual Reproduction

Genetic Engineering

How it all begins • Sexual Reproduction: – Two cells from different parents unite to produce the first cell of the new organism Examples: Multicellular organisms; trees , birds, humans Consequences: No control of what two parents come together to make offspring. * Allows for variations that can lead to adaptation or defects

Crossing Over • Crossing Over: Occurs during prophase I of Meiosis • Homologous chromosomes pair up and form tetrads • Results in the exchange of alleles between homologous chromosomes, and produces new combinations of alleles. • *Normally equal sharing, if unequal, it can lead to duplication or deletion of chromosomal segments

Back to Mendel… • Segregation of alleles: During gamete formation alleles are segregated from each other so that each gamete carries only a single copy of each gene. • Example: pea plants with the allele for shortness and tallness. • *Provides genetic variety, problems can arise when nondisjunction occurs. Can produce a trisomy condition

Random Fertilization • The two gametes that come together to form an organism is completely random • Any sperm has the potential to fertilize the egg

Selective Breeding Allowing only organisms with desired traits to produce offspring. Examples: Dogs – Pure Breed Show Quality Sheep - Growth Rate and Wool Qualities

Advantages/Disadvantages Perks: Allows for desired improvement of a species. Humans select traits that they find appealing. Disadvantages: Beef Cattle – Bigger cattle produces more meat. More meat = More $ “Double Muscling” (Problems with birthing) cows have a harder time birthing their young because they are too big.

Hybridization Crossing dissimilar organisms to bring together the best of both organisms Examples: Mule – Donkey and Horse Liger – Lion and Tiger Tangelo – Tangerine and Pomelo Wheat plants – Mostly hybrids Selected for ability to resist disease, weather tolerance, and produce the most grains

Advantages/Disadvantages • Sterility results in some animals which means they cannot produce offspring. • Generally will make plants hardier and more disease resistant. • Can combine disease resistance with food -producing capabilities. (Crops)

Inbreeding Continual breeding of organisms with similar characteristics Examples: Pack Animals – Lions in the same pride Many Royal Families passed around diseases – Hemophilia-when your blood does not clot. Sexlinked recessive disorder.

Advantages/Disadvantages Problem: Encounter the possibility of combining two organisms with two alleles for the same genetic defect. Small gene pool creates less variability of genes.

Inducing Mutations Humans purposely create mutations in organisms How? Using radiation and chemicals Examples: Oil eating bacteria – When oil spills occur scientists have developed bacteria that can digest oil, turning it into methane gas. These bacteria quickly and efficiently clean up the spill caused by mankind.

Advantages/Disadvantages New mutants can help to solve some problems, but new problems can arise from the induced mutations. Sometimes taking over ecosystems and destroying food webs.

Polyploidy Deffinition: Organisms with many sets of chromosomes. How? Use of drugs to stop chromosomal segregation during meiosis. This leaves organism with double or triple number of chromosomes. (Don’t forget it can also happen naturally) Examples: Plants – Flowers, Fruits, Etc. Animals – Usually fatal (downs syndrome)

A Polyploid Clone

Advantages/Disadvantages Problem in humans, polyploidy can lead to miscarriages. Makes plants stronger and larger. Bigger plants = more $$ for farmers Triploid crops: banana, apple, watermelon, citrus Tetraploid crops: wheat, corn, cotton, potato, tobacco Hexaploid crops: wheat Octaploid crops: strawberry