Question

A cross was carried out between plant hrtrozygous for round and yellow seed with a pea plant having wrinkled green.Comseed

Answer 1

If an organism is heterozygous and for this case the plant is heterozygous what is meant is that it posses one of each allele and the dominant trait is expressed.

for this question we consider dihybrid inheritance or cross.

Let R represent allele for Round seed

Let r represent allele for wrinkled seed

Let Y represent allele for Yellow colour

let y represent allele for green colour

The genotype for the plant having round and yellow seed but heterozygous is RrYy that of wrinkled green is rryy. Then the gametes to be used for crossing will be;

for round yellow plant is: RY, Ry, rY, ry

that of wrinkled green is ry, ry, ry, ry

when these gametes are put in a punnet square, 16 offsprings results leading to a dihybrid ratio of 9:3:3:1

Do not confuse it with the monohybrid ratio of 3:1