Suppose that in plants, smooth seeds (S) are dominant to wrinkled seeds (s) and tall plants (T) are dominant to short plants (t).A tall plant with smooth seeds was backcrossed to a parent that was short and wrinkled.What proportion of the progeny is expected to be heterozygous for tall and smooth?
A)1/2
B)1/4
C)1/8
D)1/16
E)0

Question

Quizplus · Accepted Answer

The tall plant with smooth seeds must be TtSs (heterozygous for both traits). The parent that was short and wrinkled is ttss (homozygous recessive for both traits). When these two individuals are crossed, the heterozygous TtSs parent can produce four types of gametes: TS, Ts, tS, and ts. The homozygous recessive parent can only produce one type of gamete: ts. 
Therefore, the potential genotypes of the offspring are TtSsts, TtSsts, Ttss, Ttss, ttSs, ttSs, ttss, ttss. 
Out of these eight possible genotypes, only two have the heterozygous TtSs genotype: TtSsts and TtSsts. Thus, the proportion of the progeny expected to be heterozygous for both traits is 2/8 or 1/4.

Suppose That in Plants, Smooth Seeds (S) Are Dominant to Wrinkled