Question

Which of the following statements are correct?
i. $X$ chromosome has large amount of euchromatin.
ii. heterochromatin is genetically inert.
iii. Both X and Y chromosomes are homologous.
iv. Crossing over does not take place in sex chromosomes in female.
Choose the correct option.

• A. i and ii only
• B. ii and iii only
• C. i, ii and iii only
• D. iv and v only

Hint:

Key facts: Euchromatin $\rightarrow$ Active Heterochromatin $\rightarrow$ Inactive XX $\rightarrow$ Crossing over occurs

Answer 1

The Correct Option is A

Concept: Chromatin exists in two forms:
• Euchromatin: Active, loosely packed
• Heterochromatin: Inactive, densely packed

Step 1: Analyze statement i.
X chromosome contains large amount of euchromatin. Correct.

Step 2: Analyze statement ii.
Heterochromatin is genetically inactive (inert). Correct.

Step 3: Analyze statement iii.
X and Y chromosomes are not fully homologous (only partially homologous). Incorrect.

Step 4: Analyze statement iv.
Crossing over occurs in female (XX chromosomes). Incorrect.

Step 5: Conclusion.
Correct statements are i and ii only. Final Answer: Option (A)