Inheritance of One Gene - Free MCQ Practice Test with solutions, NEET Biology

Self-pollination leads to fertilization by the pollen from the same flower. A cross desires pollination and fertilization by pollen from a different plant. Hence self-pollination needs to be avoided.

In a self-cross of heterozygous violet-flowered pea plants (Vv), the Punnett square for the flower color gene would yield the following genotypic and phenotypic ratios:

Genotypic Ratio: 25% VV (violet), 50% Vv (violet, but carrying the white allele), 25% vv (white)
Phenotypic Ratio: 75% violet and 25% white

This means that 75% of the offspring would have violet flowers, and 25% would have white flowers. Therefore, the correct answer is option D, "75% violet and 25% white.

Mendel's Law of Dominance states that in a pair of alleles, one may mask the expression of the other. The third option (C) cannot be explained by this law because the Law of Dominance does not address the concept of blending or recovery of both characters in the F2 generation. Instead, it focuses on how dominant traits mask recessive traits, and the characters appear as distinct and separate in the F2 generation.
 

The F2 progeny has both dwarf and tall plants. 25% of them are homozygous tall, 50% are heterozygous tall, and 25% are homozygous dwarf. Dwarfness is a recessive trait and thus cannot be expressed in the heterozygous state.

The ratio of tall to dwarf plants in the offspring (90:30) indicates a 3:1 phenotypic ratio typical of a cross between two heterozygous tall plants (Tt x Tt). Thus, the parents must have been Tt and Tt.

Heterozygosity refers to different alleles present at a given locus. This is the condition that is of interest to the study of genetics. It can be used to test the nature of an allele.

Yellow being recessive will express only when both alleles are present. That occurs only when both parents can contribute an allele encoding for the yellow pod. For all progeny to have yellow pods, both parents have to be homozygous for yellow pods.