Let P = purple flowers and p = white, and T = tall plants and t = dwarf. What are the genotypes of the gametes that are produced by a plant that is heterozygous for both traits?

Question

A.  PpTt only
B.  PT and pt
C.  P, p, T, and t
D.  PT, Pt, pT, and pt
E.  Tt, TT, tt, Pp, PP, and pp

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? How does it relate to the question?

Consider Possibilities
· Are other answers plausible?

Choose Answer
· Given what you now know, what 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

D.  PT, Pt, pT, and pt

Clarify Question
· What is the key concept addressed by the question?
        o This question requires two steps. First, you must determine the genotype of a plant that is heterozygous for the two genes—then you can decide what gametes that plant will produce.
· What type of thinking is required?
        o You need to use your understanding of heterozygosity and independent assortment, and Apply it to a plant with this particular set of genes.
· What key words does the question contain?
        o The plant is heterozygous for both traits – it carries two alleles for each gene. The question asks which gametes, or germ cells, are produced.

Gather Content
· What do you already know? How does it relate to the question?
        o A diploid organism has two copies of each gene. In this case, it is heterozygous for both genes – it has two different alleles for each. So the plant is Pp Tt.
        o Gametes are haploid and carry only one allele for each gene. They assort independently (unless you have reason to believe that they are linked on a chromosome). So any gamete may receive P or p, and any gamete may receive T or t.
        o This creates four possible combinations: PT, Pt, pT, and pt.

Consider Possibilities
· Are other answers plausible?
        o The gametes must be haploid and carry only one copy of each gene. So you can eliminate answers that have “Pp”, etc.
        o A gamete must also contain a copy of every gene. So each gamete must have P or p, plus a T or t.
        o Finally, you know that genes assort independently. So there are four types of possible gametes, not just PT and pt.

Choose Answer
· Given what you now know, what approach is most likely to produce the correct answer?
        o Determine the genotype of the double heterozygous plant. Then determine every possible combination of the four alleles to describe the gametes.

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 You will benefit from reading slowly and carefully. This question required determining the plant genotype before figuring out the gametes produced.