1. Epistasis is the control of a phenotype by two or more interacting genes. In a dominant epistatic model, one gene can mask the effect of the second gene, leading to the expression of one main phenotype and two rarer phenotype variants. Geneticists examined the distribution of seed coat color in cultivated amaranth grains. Crossing black-seeded and pale-seeded populations gave the following counts of black, brown, and pale seeds in the second generation.
Seed Coat Color
|
Black
|
Brown
|
Pale
|
Seed Count
|
321
|
77
|
31
|
a. According to the laws of genetics, dominant epistasis should lead to a 12:3:1 distribution in the second generation of black:brown:pale. For a chi-squared goodness-of-fit test, what would the null and alternative hypotheses be if you wanted to test if this is true?
b. Write out the expected counts under the null hypothesis and calculate the chi-squared test statistic. Calculate a p-value and make a decision.
c. Write your conclusion.
Suppose 2% of all babies are born with green eyes. Out of 8 randomly selected babies born in a specific day, what is the probability that:
a. Three or more babies are green-eyed.
b. Exactly 2 babies are green-eyed.