Which of the following statements about genes responsible for X linked disease inheritance is/are TRUE?
1: They are located on the X chromosome.
2: They are passed on from mother to female child only.
3: They are passed to all male offsprings from male parent.
4. They are passed to all male offsprings from affected mother.

Options

A. only 1
B. only 1 and 4
C. only 2, 3 and 4
D. only 1, 2 and 3

Answer

To determine which statements about genes responsible for X-linked disease inheritance are true, we will evaluate each statement one by one.

### Step-by-Step Solution:

1. **Statement 1: They are located on the X chromosome.**
- **Evaluation**: This statement is true. X-linked diseases are caused by mutations in genes located on the X chromosome. Therefore, this statement is correct.

2. **Statement 2: They are passed on from mother to female child only.**
- **Evaluation**: This statement is false. While mothers can pass on X-linked genes to their daughters, they can also pass them to their sons. Sons inherit their X chromosome from their mother and their Y chromosome from their father. Therefore, this statement is incorrect.

3. **Statement 3: They are passed to all male offspring from male parent.**
- **Evaluation**: This statement is false. Males inherit their X chromosome from their mother and their Y chromosome from their father. Therefore, a male parent does not pass on an X chromosome to his sons. This statement is incorrect.

4. **Statement 4: They are passed to all male offspring from affected mother.**
- **Evaluation**: This statement is true. If the mother is affected by an X-linked disorder, she has one or two affected X chromosomes. Each son will inherit one X chromosome from the mother, which is likely to be affected if the mother has the disorder. Therefore, this statement is correct.

### Conclusion:
Based on the evaluations:
- **True Statements**: 1 and 4
- **False Statements**: 2 and 3

### Final Answer:
The true statements about genes responsible for X-linked disease inheritance are **1 and 4**.

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