Question

Match List-I with List-II

List-I (Particulars) & List-II (Nomenclature)
(A) An increase in the size of the triplet repeat & (I) Frameshift mutation
(B) A 5 bp deletion in an exon & (II) Transversion
(C) Substitution of one amino acid for another & (III) Expansion
(D) An A to a T point mutation & (IV) Missense mutation

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

Hint:

To solve mutation matching questions quickly:
- Transition = Purine to Purine (A $\leftrightarrow$ G) or Pyrimidine to Pyrimidine (C $\leftrightarrow$ T).
- Transversion = Purine to Pyrimidine (A/G $\leftrightarrow$ C/T).
- Deletions/Insertions not divisible by 3 = Frameshift.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
To match the genetic mutations correctly, we must define the different types of molecular mutations based on their effects on DNA sequences and polypeptide chains.

Step 2: Detailed Explanation:
Let us analyze each pair:
- (A) An increase in the size of the triplet repeat $\rightarrow$ (III) Expansion:
This refers to trinucleotide repeat expansion, where a sequence of three nucleotides repeats multiple times and increases in copy number during DNA replication. This is responsible for disorders like Huntington's disease.
- (B) A 5 bp deletion in an exon $\rightarrow$ (I) Frameshift mutation:
An exon is a protein-coding region.
Since the genetic code is read in triplets, any insertion or deletion of nucleotides that is not a multiple of three (such as a 5 bp deletion) alters the reading frame of the mRNA during translation, leading to a frameshift mutation.
- (C) Substitution of one amino acid for another $\rightarrow$ (IV) Missense mutation:
A point mutation that alters a single codon such that it codes for a different amino acid in the resulting protein is called a missense mutation.
- (D) An A to a T point mutation $\rightarrow$ (II) Transversion:
Adenine (A) is a purine, and Thymine (T) is a pyrimidine.
A mutation that replaces a purine with a pyrimidine (or vice versa) is classified as a transversion.
Matching these pairs gives: (A)-(III), (B)-(I), (C)-(IV), (D)-(II).

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