Find odd one out. W.r.t codominance.

Options

A. Heterozygous sickle celled individual
B. AB blood group
C. MN blood group
D. Flower colour in Pisum

Answer

### Step-by-Step Solution:

1. **Understanding Co-dominance**: Co-dominance is a genetic phenomenon where both alleles in a heterozygous individual are fully expressed, resulting in offspring with a phenotype that is neither dominant nor recessive.

2. **Analyzing the Options**:
- **Option 1: Heterozygous Sickle Cell Individual**: In this case, the individual has both normal hemoglobin (A) and sickle hemoglobin (S). Both types of hemoglobin are produced, making this an example of co-dominance.
- **Option 2: AB Blood Group**: The AB blood group is formed by the presence of both IA and IB alleles. Both alleles are expressed equally, which is a classic example of co-dominance.
- **Option 3: MN Blood Group**: Similar to the AB blood group, the MN blood group is determined by the presence of both M and N alleles. Both alleles are expressed, making this another example of co-dominance.
- **Option 4: Flower Color in Pisum**: In Mendelian genetics, flower color in Pisum (pea plants) typically shows a dominant-recessive relationship (e.g., purple is dominant over white). This means that only one allele is expressed in the phenotype, which does not fit the definition of co-dominance.

3. **Identifying the Odd One Out**: Based on the analysis, the flower color in Pisum is the only option that does not demonstrate co-dominance. It is an example of simple dominance rather than co-dominance.

4. **Conclusion**: The odd one out with respect to co-dominance is **Option 4: Flower Color in Pisum**.