Question

Three Mark Questions :
Two independent monohybrid crosses were carried out involving a tall pea plant with a dwarf pea plant. In the first cross, offspring population had equal number of tall and dwarf plants, whereas in the second cross it was different. Work out the crosses and explain giving reasons for the difference in the offspring populations.

Answer 1

It the plant has a heterozygous genotype of Tt and the dwarf a homozygous genotype of tt. Under such conditions, the resulting progenies will have either the T or t allele from one parent and the t allele from the other. This will result in either a genotype of Tt (tall) or tt (dwarf) and both of them will be 50%. The cross can be shown as in the image. However, if the tall plant has a homozygous genotype of TT then all the progenies will have a heterozygous genotype of Tt and will be tall. Since in such cases the tall plant will transfer the allele T and the dwarf plant the allele t, giving the progeny a heterozygous genotype of Tt.