Question

Match List-I with List-II:
\includegraphics[width=0.6\linewidth]{23.png Choose the correct answer from the options given below:

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

Hint:

To quickly solve mutation matching questions, use clear definitions:
No amino acid change = Silent (I).
Increased/new activity = Gain-of-function (II).
Disturbs wild-type in heterozygote = Dominant negative (IV).

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Mutations are alterations in the nucleotide sequence of DNA.
Based on their phenotypic consequences and biochemical effects on the gene product, mutations are classified into specific functional categories such as silent, loss-of-function, gain-of-function, and dominant-negative.

Step 2: Detailed Explanation:
Let us correlate the biological situations in List-I with their genetic nomenclature in List-II:
1. A point mutation that leads to failure of expression of one allele (A):
When a mutation causes an allele to produce a non-functional protein or completely prevents its transcription/translation, it is termed a loss-of-function mutation (often resulting in a null allele).
Thus, (A) matches with (III).
2. A point mutation that does not alter the encoded amino acid (B):
Due to the degeneracy of the genetic code, multiple codons can specify the same amino acid.
A nucleotide substitution that changes a codon to another synonym codon does not alter the primary structure of the protein. This is called a silent mutation.
Thus, (B) matches with (I).
3. A mutation which also results in the disturbance of the activity of the normal gene or protein (C):
Some mutant proteins form multimeric complexes with wild-type subunits and actively disrupt the function of the remaining normal subunits.
This is known as a dominant negative effect (or antimorph mutation).
Thus, (C) matches with (IV).
4. A mutation that results in different or increased protein activity (D):
A mutation that confers a new activity on a protein or increases its normal expression/activity is classified as a gain-of-function mutation.
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 (B).