Question

Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R
Assertion A: X chromosome is acrocentric and Y chromosome is submetacentric.
Reason R: This is based on the position of centromere on the chromosome.

• A. Both A and R are correct and R is the correct explation of A
• B. Both A and R are correct but R is NOT the correct explation of A
• C. A is correct but R is not correct
• D. A is not correct but R is correct

Hint:

Human Chromosomes:
Human X chromosome = Submetacentric.
Human Y chromosome = Acrocentric.
Human Acrocentric chromosomes = 13, 14, 15, 21, 22, and Y.

Answer 1

The Correct Option is D

Step 1: Understanding the Question:
The question tests knowledge regarding human sex chromosome morphology (centromere positioning) and chromosome classification definitions.

Step 2: Key Formula or Approach:
Chromosomes are classified according to the relative location of their centromere:
• Metacentric: Centromere in the middle; equal $p$ and $q$ arms.

• Submetacentric: Centromere slightly off-center; unequal arms ($p < q$).

• Acrocentric: Centromere near one end; very short $p$ arm.

• Telocentric: Centromere at the extreme termil tip.

Step 3: Detailed Explation:

• Alysis of Assertion A: In human karyotyping:
• The X chromosome is a medium-sized submetacentric chromosome (Group C).

• The Y chromosome is a small acrocentric chromosome (Group G).
Assertion A claims the exact opposite (stating X is acrocentric and Y is submetacentric), which is factually incorrect. Thus, Assertion A is not correct.

• Alysis of Reason R: Chromosomes are universally classified into metacentric, submetacentric, acrocentric, or telocentric categories based directly on the position of the centromere along the chromosome length. Thus, Reason R is correct.

Step 4: Fil Answer:
Assertion A is not correct, but Reason R is correct.