$ Sicke cell anaemia is a type of pleiotropy.
! Sex linked inharitance is also called criss cross inheritance.

Options

A. If both As and R are correct and R is correct explanation of As
B. If both As and R are correct but R is not correct explanation of As
C. If As is correct, R is wrong
D. If both As and R are wrong.

Answer

To solve the question regarding sickle cell anemia and sex-linked inheritance, we can break it down into the following steps:

### Step 1: Understanding Sickle Cell Anemia
- **Definition**: Sickle cell anemia is a genetic disorder caused by a mutation in the hemoglobin gene.
- **Pleiotropy**: This condition is an example of pleiotropy, where one gene affects multiple phenotypic traits. In sickle cell anemia, the mutation leads to the production of abnormal hemoglobin, which causes red blood cells to assume a sickle shape, leading to various health complications.

### Step 2: Analyzing the Assertion
- **Assertion**: "Sickle cell anemia is a type of pleiotropy."
- **Evaluation**: This statement is true because the mutation in a single gene (the hemoglobin gene) results in multiple effects on the body, such as pain crises, anemia, and increased susceptibility to infections.

### Step 3: Understanding Sex-Linked Inheritance
- **Definition**: Sex-linked inheritance refers to traits that are associated with genes located on sex chromosomes (X and Y).
- **Crisscross Inheritance**: This term describes how traits are passed from parents to offspring through the sex chromosomes. For example, if a mother carries a recessive trait on one of her X chromosomes, she can pass this trait to her son, while her daughters may become carriers.

### Step 4: Analyzing the Reason
- **Reason**: "Sex-linked inheritance is also called crisscross inheritance."
- **Evaluation**: This statement is also true. The term "crisscross inheritance" accurately describes how traits can be inherited through the sex chromosomes, with males receiving their X chromosome from their mothers and females receiving their X chromosome from both parents.

### Step 5: Conclusion
- Both the assertion and the reason are correct. However, they refer to different genetic concepts (sickle cell anemia and sex-linked inheritance). Therefore, while both statements are true, the reason does not explain the assertion.

### Final Answer
The correct option is: **Both assertion and reason are correct, but the reason is not the correct explanation of the assertion.**

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