Question

. In pea plants, the allele for tall plants (T) is dominant to the allele for short plants (t). You observe that the offspring of a cross include 78 tall plants and 27 short plants. a. What was the probable allele combination of the two parent plants? b. How would your answer change if the offspring included 121 tall plants and 118 short plants?

Answer 1

a) Genotype of each parent plant= Tt

b) Genotypes of parent plants= Tt and tt

Step-by-step explanation:

a) In the first cross, the tall and short progeny was obtained in almost a 3:1 ratio (78: 27). This means that both the parent plants were heterozygous for the gene of plant height. The genotype of each of the parents was Tt. A cross between Tt and Tt gives following progeny ratio=

Tt x Tt = 3 tall (1/2 TT and 1/4 Tt) : 1 short (1/4 tt)

b) In the second cross, tall and short progeny was obtained in almost a 1: 1 ratio (121: 118). This means that one parent plant was homozygous recessive (tt) and the other was heterozygous dominant (Tt).

Tt x tt = 1 tall: 1 short.