In pea plant, spherical seeds (S) is dominant to dented seeds(s). In a genetic cross of two plants that are heterozygous for seed shape trait, what fraction of the offspring should have spherical seeds ?
Answers
In pea plant where spherical seeds (S) is dominant to dented seeds (s), the cross between two plants that are heterozygous for seed shape trait gives 3/4 of plants having spherical seeds.
This idea of crossing follows Mendelian fashion with 3:1 monohybrid ratio.
When crossing of a heterozygous plant with reference to seed shape, that is to say that the alleles responsible for seed shape are not the same. The cross gives the following offsprings; SS, Ss, Ss, ss. Spherical gene trait being dominant over dented seed shape 3 of the offspring will have spherical shape and one offspring will have dented shape.
While crossing a pea plant for seed shape trait having two forms, S for spherical seeds and s for dented seeds and (S) is dominant over (s). So, if we are crossing two heterozygotes parent plants mean that their genotypes are Ss, than we are going to have off-springs with SS, Ss, Ss, ss genotypes and (S) is dominant over (s), hence fraction of offspring with spherical seeds will be ¾ i.e. 75% and the fraction of offspring with dented seeds will be ¼ i.e. 25%.