Question

A homozygous inflated pod shape variety of pea plant (I) is crossed with a constricted variety of pea plant (i) Answer the question that follows :
Sate the Mendel's law of dominance.

Answer 1

• For pod shape in pea plant inflated pod, the shape is a dominant trait whereas constricted pod shape is a recessive trait.
• Let P be the inflated pod shape and p be the constricted pod shape
• When the homozygous plants for both the traits are crossed

P PP x pp

P P p p (gametes produced)

F1 Pp x Pp (self-fertilization)

P p P p (gametes produced )

F2 P p

P PP Pp

p Pp pp

• When the homozygous parents for both the traits have crossed the progeny in the F1 generation are all having inflated pod shape which is the dominant trait even in the heterozygous condition.
• When the individuals of the F1 generation are self-fertilized then the progeny in the F2 generation is produced in a phenotypic ratio of 3:1 where 3 individuals are showing dominant trait and 1 individual is showing recessive trait. The genotypic ratio is 1:2:1, as there is one homozygous individual for each dominant and recessive trait whereas 2 individual for the heterozygous dominant trait.
• Mendel's law of dominance is as follows:

For every trait, 2 factor or alleles are passed down from parent to the children but only one of the two factors is expressed and the other one is not expressed. The factor that is expressed is dominant and the one that is not expressed is the recessive trait.

• A dominant trait is expressed in both heterozygous and homozygous condition. While recessive trait is expressed only in recessive condition.