What will be the distribution of phenotypic features in the first filial generation if a cross is carried out between a homozygous female and a heterozygous male for a single locus ?

Options

A. `1:0`
B. `1:2:1`
C. `1:1`
D. both (A) and (C)

Answer

To solve the problem of the phenotypic distribution in the first filial generation (F1) from a cross between a homozygous female and a heterozygous male for a single locus, we can follow these steps:

### Step 1: Define the Genotypes
- Let’s denote the dominant trait as "T" (tall) and the recessive trait as "t" (dwarf).
- The homozygous female can either be:
- Homozygous dominant (TT) - tall
- Homozygous recessive (tt) - dwarf
- The heterozygous male will be (Tt).

### Step 2: Consider Both Cases for the Female
1. **Case 1: Female is Homozygous Dominant (TT)**
- Female (TT) can only produce gametes with T.
- Male (Tt) can produce two types of gametes: T and t.
- Possible combinations in F1 generation:
- TT (from T of female and T of male)
- TT (from T of female and t of male)
- All offspring will be tall (phenotype: tall).
- **Phenotypic Ratio:** 100% tall.

2. **Case 2: Female is Homozygous Recessive (tt)**
- Female (tt) can only produce gametes with t.
- Male (Tt) can produce two types of gametes: T and t.
- Possible combinations in F1 generation:
- Tt (from T of male and t of female)
- tt (from t of male and t of female)
- Offspring will be:
- 50% tall (Tt)
- 50% dwarf (tt)
- **Phenotypic Ratio:** 1 tall : 1 dwarf.

### Step 3: Conclusion
- From the two cases considered:
- If the female is homozygous dominant (TT), all offspring are tall.
- If the female is homozygous recessive (tt), half of the offspring are tall and half are dwarf.
- Therefore, the answer to the question is that the distribution of phenotypic features in the F1 generation will be either all tall or a 1:1 ratio of tall to dwarf, depending on the genotype of the female.

### Final Answer
The answer to the question is **D: both A and C** (where A represents all tall offspring and C represents a 1:1 ratio of tall to dwarf).

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