$ The two strands of a chromosome are called sister chromatids
! The two sister chromatids get separated during Anaphase.

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

### Step-by-Step Text Solution:

1. **Understanding Chromosomes**:
- Chromosomes are structures within the cell nucleus that contain genetic material. They are made up of DNA and proteins and are crucial for the inheritance of traits.

2. **Sister Chromatids**:
- Each chromosome consists of two identical halves known as sister chromatids. These chromatids are joined together at a region called the centromere.

3. **Centromere**:
- The centromere is the point where the two sister chromatids are attached. It is also referred to as the primary constriction of the chromosome.

4. **Cell Division and Anaphase**:
- During cell division, specifically in the anaphase stage, the sister chromatids are separated. This is a critical process as it ensures that each daughter cell receives an identical set of chromosomes.

5. **Movement of Chromatids**:
- Once separated, the sister chromatids move towards opposite poles of the cell. This movement is facilitated by the spindle fibers that are attached to the centromeres.

6. **Conclusion**:
- Both the assertion that the two strands of a chromosome are called sister chromatids and the reason that they get separated during anaphase are correct. However, the reason does not serve as a correct explanation for the assertion.

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

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