How would you test a Pea plant whether it is a pure or hybrid for tallness?

Options

A. Cross it with another tall Pea plant of unknown genotype
B. Cross it with a pure tall Pea plant
C. Cross with a homozygous dwarf Pea
D. Cross it with any Pea plant.

Answer

To test whether a pea plant is pure or hybrid for tallness, you can follow these steps:

### Step-by-Step Solution:

1. **Understand the Genotypes**:
- Tallness in pea plants is determined by the dominant allele (T) and the recessive allele (t). A pure tall plant has the genotype TT (homozygous dominant), while a hybrid tall plant has the genotype Tt (heterozygous).

2. **Choose a Test Cross**:
- To determine the genotype of the tall pea plant, perform a test cross. This involves crossing the tall plant (unknown genotype) with a homozygous recessive dwarf plant (tt).

3. **Perform the Cross**:
- Cross the tall pea plant (T?) with a homozygous dwarf plant (tt). The dwarf plant will always contribute a recessive allele (t).

4. **Analyze the Progeny**:
- Observe the offspring (F1 generation) from this cross:
- If all offspring are tall, it indicates that the tall plant was pure (TT).
- If the offspring show a 1:1 ratio of tall to dwarf plants (50% tall and 50% dwarf), it indicates that the tall plant was hybrid (Tt).

5. **Conclusion**:
- Based on the phenotypic ratio of the offspring, you can conclude whether the original tall plant was pure or hybrid.