Which of the following is / are correct for the inheritance of genes involved in human 'ABO blood grouping?
l. It is inherited by complete dominant allele
ll. It is inherited by complete recessive allele.
III. It is inherited by co-dominant allele
IV. It is inherited by single gene with more than two alleles.

Options

A. I and II only are correct
B. II and III only are correct
C. III and IV only are correct
D. l,ll, III and IV are correct

Answer

To solve the question regarding the inheritance of genes involved in human ABO blood grouping, we will analyze each statement provided:

1. **Statement I: It is inherited by complete dominant allele.**
- In ABO blood grouping, the alleles IA (type A) and IB (type B) are dominant over the allele i (type O). Therefore, when either IA or IB is present with i, the blood group will be A or B, respectively. This statement is partially correct because while IA and IB are dominant, they do not represent complete dominance over each other.

2. **Statement II: It is inherited by complete recessive allele.**
- The allele i is indeed a recessive allele. An individual must have two copies of the i allele (ii) to express the O blood group. So, this statement is correct.

3. **Statement III: It is inherited by co-dominant allele.**
- The alleles IA and IB are co-dominant. When both alleles are present (IAIB), they express both A and B antigens on the surface of red blood cells, resulting in blood group AB. This statement is correct.

4. **Statement IV: It is inherited by a single gene with more than two alleles.**
- The ABO blood group is controlled by a single gene (the ABO gene) that has three alleles: IA, IB, and i. This means that this statement is also correct.

### Conclusion:
All four statements regarding the inheritance of genes involved in human ABO blood grouping are correct.

### Final Answer:
**All statements (I, II, III, IV) are correct.**

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