Question

Assertion (A): The loss or gain of a segment of DNA results in alteration of chromosomes.
Reason (R): Genes are known to be located on chromosomes alteration leads to aberrations.

• A. Both (A) and (R) are correct and (R) is the correct explanation to (A)
• B. Both (A) and (R) are correct but (R) is not correct explanation for (A)
• C. (A) is correct (R) is wrong
• D. (A) is wrong (R) is correct

Hint:

Chromosomal aberrations include deletions, duplications, inversions, and translocations.
They alter gene order or dosage, often resulting in severe genetic disorders or malignancies.

Answer 1

The Correct Option is A

Step 1: Confirm the Assertion.
Chromosomes carry DNA in a linear order, so losing a segment (deletion) or gaining one (duplication) genuinely changes the chromosome's structure and content. A is true.
Step 2: Confirm the Reason.
Genes sit at fixed positions along the chromosome, so any structural change to the DNA directly disturbs those gene locations, producing an aberration. R is also true.
Step 3: Connect the two.
Because genes are physically located on chromosomes, any gain or loss of a DNA segment necessarily rearranges gene positions, which is precisely why the chromosome is said to be altered. R directly accounts for A.
Final answer: Option 1, Both A and R are correct, and R correctly explains A.