Which of the following statements is / are correct for a polygenic inheritance ?
1. They show uniformity.
2. Controlled by three or more genes.
3. It is not influenced by the environment .
In polygenic inheritance, phenotype reflects the contribution of recessive allele only .

Options

A. 1 and 2
B. 2 , 3 and 4
C. 1, 3 and 4
D. only 2

Answer

To solve the question regarding polygenic inheritance, we will analyze each statement one by one.

### Step-by-Step Solution:

1. **Statement 1: They show uniformity.**
- **Analysis:** Polygenic traits do not show uniformity because they exhibit a range of phenotypes. For example, in human height, individuals can be tall, medium, or short, and there are many variations within these categories. Therefore, this statement is **incorrect**.

2. **Statement 2: Controlled by three or more genes.**
- **Analysis:** This statement accurately describes polygenic inheritance. Polygenic traits are indeed controlled by three or more genes. For instance, traits like height and skin color are influenced by multiple genes. Therefore, this statement is **correct**.

3. **Statement 3: It is not influenced by the environment.**
- **Analysis:** This statement is incorrect. Polygenic traits can be influenced by environmental factors. For example, skin color can change due to sun exposure (tanning), and height can be affected by nutrition and health. Hence, this statement is **incorrect**.

4. **Statement 4: In polygenic inheritance, phenotype reflects the contribution of recessive alleles only.**
- **Analysis:** This statement is also incorrect. In polygenic inheritance, the phenotype is typically influenced by both dominant and recessive alleles. While recessive alleles can contribute to the phenotype, they do so primarily when in a homozygous condition. In most cases, dominant alleles have a more significant impact on the phenotype. Therefore, this statement is **incorrect**.

### Conclusion:
- The only correct statement regarding polygenic inheritance is **Statement 2**.

### Final Answer:
- **Only Statement 2 is correct.**