Question

Mendel deduced the genetic principle of inheritance by experimenting on sweet pea plants. One of the experiments involved crossing plants with two contrasting characters, tall (dominant) and dwarf (recessive), which yielded all tall plants in the first generation. When the same genetic cross was independently repeated by a researcher, only short plants were obtained. Which one of the following can possibly explain the altered outcome?

• A. Tall plants were heterozygous
• B. An enhancer for the tall allele is present in the dwarf plant
• C. A suppressor for the tall allele is present in the dwarf plant
• D. Dwarf plants are homozygous

Hint:

A suppressor gene can interfere with the expression of other alleles, leading to altered inheritance patterns.

Answer 1

The Correct Option is C

Step 1: Understanding the genetic cross.
In Mendel's experiments, he crossed tall and dwarf plants. The tall character is dominant, and the dwarf character is recessive. The initial generation of offspring was all tall, which suggests that the tall plants were heterozygous (Tt).

Step 2: Analyzing the options.
- (A) Incorrect, the tall plants in the first generation were likely heterozygous, but this does not explain the altered outcome in the subsequent generation.
- (B) Incorrect, an enhancer for the tall allele in the dwarf plant would not cause the change in outcome.
- (C) Correct, a suppressor gene in the dwarf plant could have modified the expression of the tall allele, leading to only dwarf plants in the second generation.
- (D) Incorrect, the genotype of the dwarf plants being homozygous does not explain the altered outcome, as they should still produce tall plants when crossed with a heterozygous tall plant.
Step 3: Conclusion.
Thus, the correct answer is (C) A suppressor for the tall allele is present in the dwarf plant.