Which among the following plants produced from a dihybrid cross will have homozygous genetic compositions for both the characters?
YR
Yr
yR
yr
YR
I
V
IX
XIII
Yr
II
VI
X
XIV
yR
III
VII
XI
XV
yr
IV
VIII
XII
XVI
A
I only
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B
I, III and V only
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C
III, VII and XI only
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D
I and XVI only
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Solution
The correct option is D I and XVI only A cross between individuals with two pairs of contrasting characters is called a dihybrid cross. The offspring produced have both parental as well as new combinations of traits. This is due to the random and independent assortment of the alleles of these traits during meiosis in gametogenesis.
16 progeny formed from by the fusion of four different types of gametes from each side possess 9 different genotype and 4 different types of phenotype. Among all the possible genotype combinations, only two genotypes are homozygous for both the characters. These are: plant I- ( YR × YR⇾YYRR) which expresses the dominant phenotype; and plant XVI ( yr × yr⇾ yyrr) which expresses the recessive phenotype.