Question

In one of the hybridisation experiments, a homozygous dominant parent and a homozygous recessive parent are crossed for a trait. (Plant shows Mendelian inheritance pattern)

• A. Dominant parent trait appears in F₂ generation and recessive parent trait appears only in F₁ generation.
• B. Dominant parent trait appears in F₁ generation and recessive parent trait appears in F₂ generation.
• C. Dominant parent trait appears in both F₁ & F₂ generations, recessive parent trait appears in only F₂ generation.
• D. Dominant parent trait appears in F₁ generation and recessive parent trait appears in F₁ and F₂ generations.

Answer 1

The Correct Option is C

Step 1: Understand the cross
A homozygous dominant parent (AA) is crossed with a homozygous recessive parent (aa).
The F1 generation produced from this cross will all have the heterozygous genotype (Aa), displaying the dominant trait because the dominant allele masks the recessive allele.

Step 2: F2 generation after self-crossing of F1 plants
When the F1 generation (Aa) is crossed with each other (Aa × Aa), the F2 generation follows a typical Mendelian ratio of 3:1, where:

• 3 plants show the dominant trait (AA or Aa)
• 1 plant shows the recessive trait (aa)

Step 3: Conclusion on dominant and recessive traits
The dominant parent trait will appear in both F1 and F2 generations. The recessive parent trait will only appear in the F2 generation, when the homozygous recessive genotype (aa) is formed.

The correct answer is (C) : Dominant parent trait appears in both F₁ & F₂ generations, recessive parent trait appears in only F₂ generation.

Answer 2

In one of the hybridisation experiments, a homozygous dominant parent and a homozygous recessive parent are crossed for a trait. (Plant shows Mendelian inheritance pattern)

The correct answer is: (C) Dominant parent trait appears in both F₁ & F₂ generations, recessive parent trait appears in only F₂ generation.

In a typical Mendelian inheritance pattern, when a homozygous dominant parent (AA) is crossed with a homozygous recessive parent (aa), all the F₁ offspring will inherit one dominant allele from the dominant parent and one recessive allele from the recessive parent. Therefore, all F₁ individuals will be heterozygous (Aa) and will exhibit the dominant trait.

In the F₂ generation, obtained by crossing two F₁ individuals (Aa × Aa), the offspring will exhibit a 3:1 phenotypic ratio, where three-fourths of the offspring will show the dominant trait and one-fourth will show the recessive trait. This is because the recessive allele can only express its trait when it is present in a homozygous recessive condition (aa), which only appears in the F₂ generation.

Therefore, the dominant parent trait appears in both F₁ and F₂ generations, while the recessive parent trait appears only in the F₂ generation.