Animal Genetics & Heredity Test Review

1. Animal Genetics & Heredity Test Review Advanced Animal Science

2. 1. With whom did modern genetics begin? • Gregor Mendel

3. 2. How did this person study genetics? • By breeding garden peas • Used a true breeding white flower garden pea plant and a true breeding purple flower garden pea plant

4. 3. Define True Breeding • A kind of breeding in which the parents with a particular phenotype produce offspring only with the same phenotype.

5. 4. Define hybridization. • Mating, or crossing, of two varieties.

6. 5. Define P generation. • True breeding parents

7. 6. Define F1 generation. • Hybrid offspring of the P generation • The first offspring from a cross

8. 7. Define F2 generation. • Offspring from the self-fertilization of the F1 hybrids • The offspring from mating, or crossing, individuals from the F1 generation.

9. 8. Explain what a genotype is. • The entire set of genes in a cell, an organism, or an animal.

10. 9. Explain the difference between dominant and recessive genes. • Dominant genes overshadow recessive genes when present. • Recessive genes will only show when two are present.

11. 10. What are the three basic genotypes? • Homozygous Dominant (AA) • Heterozygous (Aa) • Homozygous Recessive (aa)

12. 11. Explain what phenotype is. • The physical expression of a gene • Physical appearance of an organism as a result of its genotype

13. 12. What information is provided by a punnett square? • The frequencies of the different genotypes and phenotypes among the offspring of a cross • The genotypes and phenotypes possible for the offspring of a cross and the probability of each occurring

14. 13. In horses, black is dependent upon a dominant factor (B) and chestnut upon its recessive allele (b). The trotting gait is due to a dominant factor (T) and the pacing gait to its recessive allele (t). If a homozygous black pacer is mated to a homozygous chestnut trotter, what will be the appearance of the F1 generation?

15. Genotype = All BbTt or Heterozygous • Phenotype = All Black Trotters

16. 14. If a trait is considered a sex-linked trait and is only carried on the Y chromosome, which offspring will have a chance of inheriting the trait? Explain. • Only the male offspring will be able to inherit the trait because female offspring can only receive a X chromosome from the father and the mother. • Only males have a Y chromosome.

17. 15. How can genetics be improved in livestock? • Naturally—survival of the fittest • Artificially—animals with desirable traits are used in breeding programs

18. 16. What is heritability? • The capacity of a trait to be passed down from a parent to offspring

19. 17. Explain incomplete dominance and give an example seen in livestock. • Individual displays a trait that is intermediate between the two traits of the parents • Neither allele completely dominates the other • Example: Crossing a Hampshire pig with a Yorkshire pig results in a Blue Butt

20. 18. Define codominance and give an example seen in livestock. • Two dominant alleles are expressed at the same time • Both forms of the trait are displayed • Example: Roan coat pattern in horses and cattle

21. 19. Define heterosis/hybrid vigor. • Performance of the offspring is greater than the average of the parents. • Offspring are superior to the parents in many traits.

22. 20. List and explain two external environmental influences on genetics. • Temperature—heat will cause animals to eat less; some breeds are not adapted to the cold • Light—shorter days may cause lower feed consumption • Altitude—colder temperatures; decreased oxygen pressure • Humidity—some breeds are not adapted to high humidity levels • Disease—presence will decrease performance • Feed Supply—lacking = poor growth