A cross between `F_(1)` hybrid and recessive parent gives a ratio of

Options

A. `3:1`
B. `1:1`
C. `2:1`
D. `4:1`

Answer

To solve the question regarding the cross between an F1 hybrid and a recessive parent, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Terms**:
- The F1 hybrid refers to the first generation offspring resulting from a cross between two different parental lines. In this case, we are considering a dominant trait (tall) and a recessive trait (dwarf).
- The recessive parent is homozygous for the recessive trait (tt).

2. **Identify the Genotypes**:
- Let's denote the dominant allele for tallness as 'T' and the recessive allele for dwarfness as 't'.
- The F1 hybrid will be heterozygous (Tt) since it inherits one dominant allele from one parent and one recessive allele from the other.
- The recessive parent will be homozygous recessive (tt).

3. **Perform the Test Cross**:
- A test cross involves crossing the F1 hybrid (Tt) with the recessive parent (tt).
- The possible gametes from the F1 hybrid (Tt) are T and t, while the recessive parent (tt) can only produce t gametes.

4. **Determine the Offspring Genotypes**:
- The combinations of gametes from the test cross will yield the following genotypes:
- T (from F1) and t (from recessive) → Tt (tall)
- t (from F1) and t (from recessive) → tt (dwarf)
- Therefore, the offspring genotypes will be:
- 50% Tt (tall)
- 50% tt (dwarf)

5. **Calculate the Phenotypic Ratio**:
- The phenotypic ratio of the offspring will reflect the genotypes:
- 1 tall (Tt): 1 dwarf (tt)
- This gives us a ratio of 1:1.

6. **Conclusion**:
- The ratio of the offspring from the cross between the F1 hybrid and the recessive parent is 1:1.

### Final Answer:
The ratio of the offspring from a cross between an F1 hybrid and a recessive parent is **1:1**.

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