Biology questions about genotype, phenotype, offsprings....etc. PART IV?

Question

14. A couple has three children, all of whom have brown eyes and blond hair. Both parents are homozygous for brown eyes (BB) but one is a blond (rr) and the other is a redhead (Rr). What is the probability that their next child will be a brown-eyed redhead?

a. 1/16

b. 1/8

c. 1/4

d. 1/2

e. 1

Use the information below to answer the following questions.

Feather color in budgies is determined by two different genes Y and B. YYBB, YyBB, or YYBb is green; yyBB or yyBb is blue; YYbb or Yybb is yellow; and yybb is white.

15. A blue budgie is crossed with a white budgie. Which of the following results is not possible?

a. green offspring

b. yellow offspring

c. blue offspring

d. A and B

e. A, B, and C

16. Two blue budgies were crossed. Over the years, they produced 22 offspring, 5 of which were white. What are the most likely genotypes for the two blue budgies?

a. yyBB and yyBB

b. yyBB and yyBb

c. yyBb and yyBb

d. yyBB and yybb

e. yyBb and yybb

Answer 1

14.  The phenotypes of the 3 prior children don't matter.  One parent is BBrr and the other is BBRr.  All of there children have to have brown eyes and be BB, but, their children each have a 50% chance of having red hair (Rr) or blond hair (rr).  Therefore, the anwer is 1/2 (d).

15.  Blue = yyBB or yyBb

White = yybb

No matter what, their offspring will be homozygous recessive for the Y gene.  Therefore, they cannot produce any Green or Yellow offspring, so the answer is (d).

16.  Blue budgies can be yyBB or yyBb.  If either of the budgies was yyBB, then all offspring would get a dominant B allele and would be blue.  Since they produced white offspring, then they both have to be yyBb (c).

Answer 2

14) e

15) d

16) c