1) List three individuals who historically have had an impact on Animal Breeding. Briefly describe what their contribution was.
ANSWER: Robert Bakewell – “The Father of Animal Breeding” – established the first breeding programs and consequently many breeds of animals.
Collings Brothers – apprentices to Bakewell, they continued his work and established the shorthorn cattle breed.
Jay Lush – from Iowa State, he worked with performance testing and evaluation systems.
2) Environmental improvements are temporary while genetic improvements are permanent. What does this mean? What importance does this have to Animal Breeding?
ANSWER: Environmental improvements are temporary because they cannot be passed from parent to offspring, the improvements are more individualized. Genetic improvements are permanent because they are passed from parent to offspring and can have effects for generations. The importance is to know how to deal with each and balance them to get maximum progress. Treat all animals the same for environmental improvement and keep the environment in mind when doing genetic improvements.
3) What three factors are used to determine essential traits? With one sentence each, describe them.
ANSWER: 1. The economic value of the trait will determine whether or not it is feasible to select for that trait. If an increase in the efficiency of that trait will be economically beneficial, then select for it.
2. The heritability of the trait. If the trait is worth selecting for and its heritability is high then it makes a better progress and a better choice over another.
3. The genetic correlation between the traits. We look at whether selecting for one trait automatically has an effect on another or more traits due to gene interaction and pleiotropy.
4) Discuss the relative significance to a selection program of each of the following: Sex limited, sex influenced, and sex linked traits.
ANSWER: 1. Sex limited traits – Expression of the gene (on autosome) is limited to one sex; when selecting for these traits we have to keep in mind which sex is most important to us and whether that trait will be expressed for us to see and use. It is difficult to select for the traits in the sex that doesn’t express it.
2. Sex influenced traits – Expression of the gene (on autosome) is influenced by the sex; you get one expression in the female and the opposite or other expression in the male. Easier to select for these traits because you see the traits in both sexes but also hard because the sex of the offspring will determine whether you have the expression you wanted. A selection program would not be of much significance.
3. Sex linked traits – Expression of the gene (on the sex chromosome). Easily determined on the different sexes. Not of much importance in a selection program for production traits (i.e., milk production is limited to females).