QUESTION

PLEASE ANSWER ALL WITH PUNNET SQUARES. I WILL DEFINITELY GIVE YOU A BIG THUMBS UP!!!

20. In humans, hair color is controlled by two interacting genes. The same pigment, melanin, is present in both brown-haired and blond-haired people, but brown hair has much more of it. Brown hair (B) is dominant to blond hair (b). Whether any melanin can be synthesized depends on another gene. The dominant form (M) allows melanin synthesis; the recessive form (m) prevents melanin synthesis. Homozygous recessive (mm) are albino, regardless of whether they have brown or blonde alleles. What will be the expected proportions of phenotypes in the children of the following parents? SHOW WORK FOR CREDIT, INCLUDING PUNNETT SQUARES!

a. BBMM x BbMm

b. BbMm x BbMm

c. BbMm x bbmm

21. In humans, one of the genes determining color vision is located on the X chromosome. The dominant form (C) produces normal color vision; red-green color blindness (c) is recessive. If a man with normal color vision marries a color-blind woman, what is the probability of their having a color-blind son? A color-blind daughter? SHOW WORK!!

22. In the couple described in the last problem, the woman gives birth to a color-blind but otherwise normal daughter. The husband sues for a divorce on the grounds of adultery. Will his case stand up in court? Explain. SHOW WORK FOR CREDIT

This next problem contains a sex-linked trait and a non sex-linked trait.

23. In humans, brachydactylism is the result of a dominant allele. Individuals that suffer from this trait have very short fingers. Defective dentine is also the result of a dominant allele but it is carried on the X chromosome. The allele causes the teeth to wear down rapidly and usually only stubs remain by adolescence. Assume a female who has brachydactylism and defective dentine (she is heterozygous for both traits) mates with a male who has normal fingers and teeth. SHOW WORK!

a. What is the genotype of the female? ______________

b. What is the genotype of the male? _______________

c. What kind of gametes can the female produce? __________________

d. What kind of gametes can the male produce? __________________

e. What is the probability that a son from these parents will have both brachydactylism and defective dentine? SHOW ALL WORK INCLUDING PUNNETT SQUARE!

f. What is the probability that a daughter will have both defects?

Public Answer

EPUIHF The First Answerer