Question

In rearrangement of immunoglobulin heavy chain, N-nucleotides

• A. are added by the enzyme terminal deoxynucleotidyl transferase
• B. form a palindromic sequence that is added to the end of gene segment
• C. form a palindromic sequence that is added to the single stranded end of the coding DNA
• D. are added by the enzyme DNA-dependent DNA polymerase

Hint:

Terminal deoxynucleotidyl transferase adds random nucleotides to the rearranged immunoglobulin gene segments.

Answer 1

The Correct Option is A

Step 1: Understanding Immunoglobulin Gene Rearrangement.
In the process of V(D)J recombination, the genes encoding immunoglobulins undergo rearrangement to generate diversity. N-nucleotides are added to the ends of gene segments during this process.
Step 2: Role of Terminal Deoxynucleotidyl Transferase.
Terminal deoxynucleotidyl transferase (TdT) is the enzyme responsible for adding these random N-nucleotides to the DNA ends, which contributes to diversity.
Step 3: Conclusion.
Hence, N-nucleotides are added by the enzyme terminal deoxynucleotidyl transferase, so the correct answer is (A).