John Smith breeds race horses, and he has discovered that some of the many horses on his ranch have a higher than normal metabolic rate. John believes that this would be an advantage during a race, and so he wants to selectively breed for this characteristic. Metabolic rate is a continuous character, and the average rate for all his animals is 50 units. Among his animals, the two highest rates are 88 and 80, and so he mates these two horses to each other, hoping to start a new high metabolic rate strain. Over several years, he obtains ten offspring from this cross. For each of the following sets of results (a through c), evaluate the relative contribution of genetics and environment to metabolic rate. In each case say whether it will be easy, difficult, or impossible for John to obtain his high metabolic strain, and explain your reasoning.
a) The metabolic rates of the offspring are 40, 40, 45, 49, 50, 50, 51, 55, 60, and 60.
b) The metabolic rates of the offspring are 40, 45, 49, 55, 56, 59, 60, 65, 72, 78.
c) The rates are 71, 73, 78, 80, 84, 84, 88, 90, 95, 97.
d) The presence of a white blaze on the forehead in horses is determined by a dominant allele, B. Albinism is determined by a recessive, a. A black horse with no blaze was crossed several times to an albino horse, and the F1 were all black with white blazes. What progeny, and in what proportions, would you expect to get from the cross of two of these F1 animals to each other?
e) If one of the albino F2 animals is crossed to one of the black not blazed F2 animals, what is the probability that the first offspring will be black and blazed?