A male fruit fly has the genotype PpYYrrTt. In terms of these 4 allele pairs, how many different types of gametes can he form?

Question

A.  2
B.  4
C.  8
D.  16

Clarify Question
· What is the key concept addressed by the question?
· What type of thinking is required?
· What key words does the question contain?

Gather Content
· What do you already know about alleles and gametes? How does it relate to the question?

Consider Possibilities
· What other information is related to the question? Which information is most useful?

Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?

Reflect on Process
· Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?

Answer 1

B.  4
Clarify Question
· What is the key concept addressed by the question?
        o This question asks about allele combinations in gametes.
· What type of thinking is required?
        o The question requires you to Apply your understanding of alleles and gametes to four particular genes in a fly.
· What key words does the question contain?
        o A genotype is a set of genes, and gametes are the haploid germ cells (ie, sperm in this case). Pp represents two alleles of the P gene – P and p. YY represents two alleles of the Y gene, etc.

Gather Content
· What do you already know about alleles and gametes? How does it relate to the question?
        o Gametes get one copy of each gene. Thus they get one of the alleles, randomly assorted.
        o So a gamete can get P or p for the P gene. Only Y is available for the Y gene (both alleles are the same). Only r is available for the R gene. T or t is possible for the T gene.

Consider Possibilities
· What other information is related to the question? Which information is most useful?
        o Does the choice of one allele affect the choice of the others? No. Generally speaking, genes assort independently. If genes are close together on the chromosome, they maybe linked, but this question does not indicate linkage. So the P allele can pair with either the T or t allele.

Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
        o Now it is a simple matter of counting the possible combinations. Pen and paper may be handy for this.
        o The P allele can assort with what other alleles? (Only Y, only r, and either T or t. That makes two possibilities: P Y r T and P Y r t)
        o The p allele can assort with what other alleles? (Only Y, only r, and either T or t. That makes two possibilities: p Y r T and p Y r t)
        o Add them up and you get how many total possible allele combinations? (4)

Reflect on Process
· Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
        o This question required you to Apply your knowledge and understanding to this unfamiliar situation.
        o Did you recall that each gamete receives one allele of each gene?
        o Did you recall that genes assort independently?
        o Did you use pen and paper to help figure the combinations?