You start with a population of cattle in which the heritability of body weight is 0.7. You begin a program of artificial directional selection to increase body weight. You continue this generation after generation. What will happen to the frequencies of alleles of different genes that cause an increase in body weight, and the frequencies of those allels that cause a decrease in body weight? What do you think will happen to the heritability of body weight after 20 generations of selection? Will it increasem decrease or stay the same? Explain your reasoning.