State which of the following is not true.
A. Dominance is an autonomous feature of a gene or the product that it has information for.
B. A single gene product may produce only one effect.
C. Blood group AB is an example of codominance.
D. More than tow alleles exist in a population for a single gene.

Options

A. C and D
B. A and C
C. B and D
D. A and B

Answer

To determine which statement is not true among the given options, we will analyze each statement one by one.

### Step 1: Analyze Statement A
**Statement A:** Dominance is an autonomous feature of a gene or the product that it has information for.

- **Analysis:** Dominance is not an autonomous feature. It depends on the interaction between alleles. For example, in the case of ABO blood groups, the presence of both A and B alleles results in the AB blood type, which shows co-dominance. Thus, this statement is **not true**.

### Step 2: Analyze Statement B
**Statement B:** A single gene product may produce only one effect.

- **Analysis:** This statement is incorrect because of the concept of pleiotropy, where a single gene can have multiple effects on different traits. For instance, the gene responsible for phenylketonuria affects multiple systems in the body, leading to various complications. Therefore, this statement is also **not true**.

### Step 3: Analyze Statement C
**Statement C:** Blood group AB is an example of codominance.

- **Analysis:** This statement is true. In blood group AB, both A and B alleles are expressed equally, demonstrating co-dominance. Therefore, this statement is **true**.

### Step 4: Analyze Statement D
**Statement D:** More than two alleles exist in a population for a single gene.

- **Analysis:** This statement is true as well. For example, in the case of blood types, there are three alleles (A, B, and O) that exist for the single gene controlling blood type. Thus, this statement is **true**.

### Conclusion
After analyzing all statements:
- **Statements A and B are not true.**
- **Statements C and D are true.**

### Final Answer
The statements that are not true are **A and B**.

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