Question

which one is dihybrid
a.ttrr b.ttRr c.TtRt d.Ttrr
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Answer 1

Explanation:

A dihybrid cross considers two pairs of contrasting characters. TtRr genotype is obtained from the dihybrid cross of TTRR and ttrr which are true breeding homozygous dominant and homozygous recessive breeding lines. TtRr genotype consists of both dominant and recessive alleles for two different traits. Hence, it's a dihybrid genotype.

On the other hand, other genotypes given in the questions contain heterozygous alleles for either one of the two traits of none at all.

So, the correct answer is 'TtRr'.