Mendelian Genetics

Gregor Mendel studied seven traits in his pea plant experiments, which included:

• Stem height (tall vs. dwarf) – (A)
• Pod shape (inflated vs. constricted) – (B)
• Seed shape (round vs. wrinkled) – (C)
• Seed color (yellow vs. green)
• Flower color (purple vs. white)
• Flower position (axial vs. terminal)
• Pod color (green vs. yellow)

Leaf shape was not one of the traits Mendel studied, making (D) the correct choice.

Gregor Mendel studied seven contrasting characters in pea plants (Pisum sativum). For each character, he identified one trait as dominant and the other as recessive. The dominant trait is expressed in the heterozygous condition, while the recessive trait is only expressed in the homozygous condition.

Let's examine the characters given in the options:

1. Inflated (full) pod: This concerns the pod shape. Mendel found that Inflated pod shape is dominant over constricted pod shape.
2. Green pod colour: This concerns the pod color. Mendel found that green pod color is dominant over yellow pod color.
3. White flower: This concerns the flower color. Mendel found that Violet (or Purple) flower color is dominant over White flower color. Therefore, white flower color is a recessive character.
4. Axillary flower: This concerns the flower position. Mendel found that Axial (or Axillary) flower position is dominant over terminal flower position.

Based on Mendel's findings, the only recessive character among the given options is White flower.

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.