ANSWERS

1. Why is it advantageous for breeders to be able to identify an animal carrying a recessive gene?
   Recessive genes are often unwanted, and therefore identification of animals heterozygous for a recessive gene means that breeding from such animals can be avoided.
2. How might identification of a recessive carrier be established?
   
   • Test mating to a homozygous recessive animal.
   • Test mating to a known heterozygous recessive carrier.
3. What is meant by the term "backcross to the recessive"?
   A mating to a homozygous recessive animal or a known heterozygous animal. A backcross to the recessive mating is used to reveal the presence of a recessive gene in an individual whose phenotype is the same as an animal homozygous for a dominant gene.
4. What is meant by the "first filial generation"?
   This term is used when describing a test mating, and refers to the offspring produced by the parent generation. The first filial generation may be abbreviated to the F1 generation. The F2 generation are the offspring produced by the F1 generation.
5. State Mendel's Second Law of Genetics.
   Each pair of alleles separates independently of every other pair of alleles.
6. What may cause exceptions to Mendel's Second Law?
   Linkage.
7. Describe linkage.
   Linkage describes 2 pairs of genes occurring on the same chromosome, which do not assort independently.
8. What is meant by "multifactoral inheritance"? Give an example.
   Multifactoral inheritance describes a characteristic which is influenced by a number of genes, rather than 1 gene or its alleles. An example is hip dysplasia - a number of genes interact with themselves and the environment.
9. What is the difference between a congenital and an inherited defect?
   Congenital defects are present at birth and may be inherited or due to environmental factors. Inherited defects may not be evident until some time into the life of the animal.
10. What is meant by "inbreeding"?
    Selective breeding between close family members in order to increase homozygosity and thus fix desired characteristics.
11. What is meant by "line breeding"?
    A mating within a family maintaining a relationship with a particular ancestor in order to preserve desired characteristics.
12. What is the name of the term given to the breeding of animals less closely related than those picked at random?
    Outbreeding.
13. Why might outbreeding be beneficial?
    It increases heterozygosity and introduces new genes into a population. Outbreeding masks the effects of recessive genes and results in bigger and better offspring since undesirable recessive genes are not expressed.
14. What is the main disadvantage of outbreeding?
    The offspring of an outcross will not breed true since they are heterozygous and not homozygous for their alleles.
15. What is a hybrid?
    The result of a cross conveying superiority on the heterozygote (ie. increases vigour when the parents come from different strains or species).
16. What other name might be given to hybrid vigour?
    Heterosis.