Question

Give the dihybrid cross with its phenotypic ratio.

Accepted Answer

An experimental cross between two homozygous parents in which the inheritance pattern of two pairs of contrasting characteristics is studied simultaneously is called a dihybrid cross.

For example, if the two characteristics which are to be studied are the shape and colour of the seeds of a plant then, one parent plant with round and yellow seeds that are homozygous dominant (RRYY) is crossed with the other parent that has wrinkled and green seeds (rryy) as homozygous recessive genotypes. The hybrid produced in the F₁generation will have round and yellow seeds (RrYy).

Self-pollination of the F1 generation produces four types of phenotypes in the F₂ generation. The ratio of these phenotypes in a dihybrid cross will be 9:3:3:1.

F₂generation:

Gametes
RY Ry rY ry

RY RRYY RRYy RrYY RrYy

Ry RRyy RRyy RrYy Rryy

rY RrYY RrYy rrYY rrYy

ry RrYy Rryy rrYy rryy

Phenotypic ratio: 9:3:3:1 (Yellow round: Yellow wrinkled: Green round: Green wrinkled)

Give the dihybrid cross with its phenotypic ratio.

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