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Inbreeding & Text Crossing

Genetic Engineering. Inbreeding & Text Crossing. Why is it Important?. Evaluates the importance of plant and animal breeding to humans. Because it impacts every aspect of life -Producing improved foods -Treating diseases

abigail-moore
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Inbreeding & Text Crossing

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  1. Genetic Engineering Inbreeding & Text Crossing

  2. Why is it Important? • Evaluates the importance of plant and animal breeding to humans. • Because it impacts every aspect of life -Producing improved foods -Treating diseases Most importantly, it increases the frequency of a desired allele within a population.

  3. History • For thousands of years humans have selected plants and animals with certain qualities. -Increased meat prod.; Improved milk prod. -Increased productivity (offspring) • They selectively breed them so these good qualities become common and more useful to humans. • Time, Patience, Several generations of offspring

  4. How is this done? • By Selecting • The seeds from the largest head of grain(maize) • The juiciest berry • The most disease resistant animal or plant • Raise the calves of the best milk producer • Hatch the eggs from the best egg laying hen

  5. Examples • Before Average Milk production per cow in 1947; 4997 pounds/yr • Wheat, Corn, Rice, Roses and Dahlias • After In 1997, 16,915 pounds/yr • Increased productivity in corn, Rice, Wheat • Improved color, scent and flower shape in roses.

  6. Inbreeding • Mating between closely related individuals. It results in offspring that are homozygous for most traits. Horses and Dogs have greatly benefited from inbreeding. Why? -Ensure breeds consistently exhibit a trait -Eliminate undesired traits from breeding lines -create genetic uniformity of laboratory stocks -produce stocks for crossing (animal and plant breeding) - Increased food productivity for humans

  7. Definitions • Breed: A breed is a selected group of organisms within a species bred for a particular characteristics. Example, pure bred German shepherd • It is called a cultivar in plants • Hybrids: Offspring resulting from a cross between two cultivars or closely related species are crossed.

  8. Determining Genotypes • How can a breeder learn which genotype should be used for breeding? -A good breeder is careful to determine which plant or animal has the greatest chances of transmitting or transferring a trait to the next generation. Is it homozygous dominant or heterozygous? Use TEST CROSSING

  9. Test crossing • A cross of an individual of unknown genotype with an individual of known genotype. The observed phenotype of the offspring can help determine the unknown genotype of the parent. Why do we care? To be careful and sure! Example: Disease vulnerability in roses, Progressive blindness in German shepherd dogs are all inherited as recessive traits.

  10. Possible results of a test cross • Homozygous recessive x Unknown parent = Offspring all heterozygous dominant rr x ? = Rr ,what is ? • Homozygous recessive x unknown parent = Offspring 1:1 ratio rr x ? = 1Rr : 1rr , what is ?

  11. Problem Solving • A hybrid corn is produced which is resistant to bacteria infection and is highly productive. What might have been the phenotype of the two parents? • A black mouse homozygous recessive for coat color is test crossed with a mouse of unknown genotype. All the offspring were white, what is the likely genotype of the second parent?

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