How many of following are the examples of codominance :-
(A) AB blood group
(B) Sickle cell Trait
(C) Feather colour in andalusion fowl
(D) Coat colour in cattles

Options

A. Four
B. Three
C. One
D. Two

Answer

To determine how many of the given examples illustrate codominance, we will analyze each option one by one.

### Step 1: Understand Codominance
Codominance is a genetic scenario where both alleles in a heterozygous organism are fully expressed, resulting in a phenotype that is neither dominant nor recessive. This means that both traits appear simultaneously and distinctly.

### Step 2: Analyze Each Option
- **(A) AB blood group**:
- In the AB blood group, both A and B alleles are expressed equally. Therefore, this is an example of codominance.

- **(B) Sickle cell Trait**:
- The sickle cell trait involves one normal allele (A) and one sickle cell allele (S). In this case, the heterozygous condition (AS) shows a mixture of normal and sickle-shaped red blood cells, but it is not a classic example of codominance because the sickle cell condition is more dominant in terms of health effects. Hence, this is not considered codominance.

- **(C) Feather colour in Andalusian fowl**:
- In Andalusian fowl, the feather color exhibits codominance. When a black-feathered bird is crossed with a white-feathered bird, the offspring have both black and white feathers. Thus, this is an example of codominance.

- **(D) Coat colour in cattle**:
- In cattle, when different coat colors are crossed, the resulting offspring can show patches of both colors. This is a clear case of codominance, as both parental traits are expressed distinctly.

### Step 3: Count the Examples of Codominance
Now, we summarize the findings:
- (A) AB blood group: Yes, codominance.
- (B) Sickle cell Trait: No, not codominance.
- (C) Feather colour in Andalusian fowl: Yes, codominance.
- (D) Coat colour in cattle: Yes, codominance.

### Conclusion
The total number of examples of codominance from the options provided is **3** (AB blood group, feather colour in Andalusian fowl, and coat colour in cattle).

### Final Answer
**3 examples of codominance.**

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