Question

Match List-I with List-II:
\includegraphics[width=0.6\linewidth]{24.png Choose the correct answer from the options given below:

• (A) - (III), (B) - (I), (C) - (IV), (D) - (II)
• (A) - (II), (B) - (I), (C) - (IV), (D) - (III)
• (A) - (III), (B) - (IV), (C) - (I), (D) - (II)
• (A) - (III), (B) - (IV), (C) - (I), (D) - (II)

Hint:

Remember the distinction between the two types of chromosomal inversions:
Paracentric inversion: Does not include the centromere.
Pericentric inversion: Includes the centromere (Peri = around the centromere).

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Chromosomes are organized structures of DNA and proteins.
They can undergo structural aberrations (deletions, inversions, translocations) or exhibit variation in their centromere positioning.

Step 2: Detailed Explanation:
Let us evaluate each chromosomal situation and match it with the standard cytogenetic nomenclature:
1. A chromosome that has lost material from both ends with the fusion of the sticky ends (A):
When double-strand breaks occur at both ends of a linear chromosome, the protective telomeres are lost, leaving unstable "sticky ends."
The repair machinery can fuse these two sticky ends together, forming a circular structure known as a ring chromosome.
Thus, (A) matches with (III).
2. Two chromosomes that have exchanged segments without loss or gain of any material (B):
A reciprocal translocation involves the mutual exchange of terminal segments between non-homologous chromosomes.
If there is no net gain or loss of genetic material during this exchange, it is referred to as a balanced reciprocal translocation.
Thus, (B) matches with (I).
3. A chromosome that contains a segment that has turned upside down and includes the centromere (C):
An inversion occurs when a chromosomal segment is rotated by \( 180^\circ \).
If the inverted segment contains the centromere, it is termed a pericentric inversion.
Thus, (C) matches with (IV).
4. A chromosome in which the centromere is very close to one end (D):
Chromosomes are classified based on centromere position.
In an acrocentric chromosome, the centromere is located very close to one telomeric end, resulting in one extremely short arm (p arm) and one long arm (q arm).
Thus, (D) matches with (II).

Step 3: Final Answer:
The correct matching sequence is (A)-(III), (B)-(I), (C)-(IV), and (D)-(II). This corresponds to option (A).