Test: Inheritance of One Gene - NEET MCQ

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.

F1 progeny refers to the first generation of offsprings. This is also termed as the first Filial generation, thereby stating their filial relationship with the true-breeding plants.

Emasculation is the process of removal of anthers. This is carried out to carry out pollination in a controlled manner and avoid self-pollination.

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.

Monohybrid refers to a hybrid that differs at only one gene. Thus, a plant that exhibits two alleles for one trait is a monohybrid.

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.

Violet is the dominant factor over white in pea flowers. Hence violet can express even in the presence of white. The cross of violet true-breeding and white true-breeding pea plants will produce all heterozygous offsprings. Thus, all of them will have violet flowers.

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.

Based on his studies on pea plants, he observed that the parental recessive traits were observed again only in the F2 progeny without any form of blending in F1 generation. This points out that the factors segregate or separate during the process of meiosis.

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.