Select odd one out w.r.t. autosomal recessive trait.

Options

A. Cystic fibrosis
B. PKU
C. Sickle cell anaemia
D. Colour blindness

Answer

To solve the question of selecting the odd one out with respect to autosomal recessive traits, we will analyze each option provided in the question.

### Step-by-Step Solution:

1. **Understanding Autosomal Recessive Traits**:
- Autosomal recessive traits are inherited through autosomes (non-sex chromosomes) and require two copies of the recessive allele for the trait to be expressed.

2. **Analyzing the Options**:
- **Option 1: Cystic Fibrosis**
- Cystic fibrosis is an autosomal recessive disorder caused by mutations in the CFTR gene located on chromosome 7.
- **Conclusion**: This is an autosomal recessive trait.

- **Option 2: Phenylketonuria (PKU)**
- PKU is also an autosomal recessive disorder caused by a deficiency of the enzyme phenylalanine hydroxylase.
- **Conclusion**: This is an autosomal recessive trait.

- **Option 3: Sickle Cell Anemia**
- Sickle cell anemia is caused by a mutation in the HBB gene on chromosome 11 and is inherited in an autosomal recessive manner.
- **Conclusion**: This is an autosomal recessive trait.

- **Option 4: Color Blindness**
- Color blindness is primarily an X-linked recessive disorder, meaning it is associated with genes on the X chromosome.
- **Conclusion**: This is not an autosomal recessive trait.

3. **Identifying the Odd One Out**:
- Since options 1, 2, and 3 (Cystic Fibrosis, PKU, and Sickle Cell Anemia) are all autosomal recessive traits, while option 4 (Color Blindness) is X-linked recessive, the odd one out is **Option 4: Color Blindness**.

### Final Answer:
The odd one out with respect to autosomal recessive traits is **Option 4: Color Blindness**.