Which enzyme is responsible for the addition of nucleotides during junctional diversity?

The enzyme responsible for the addition of nucleotides during junctional diversity is terminal deoxynucleotidyl transferase (TdT). This process occurs during the generation of immunoglobulins and T-cell receptors, where TdT adds non-template nucleotides at the junctions of gene segments that undergo rearrangement. This addition of nucleotides contributes to the diversity of the immune repertoire, allowing for a broad response to various antigens.

In the context of this process, TdT plays a specialized role by incorporating nucleotides without the guidance of a template strand, leading to increased variability in the final antigen receptors. This mechanism is crucial for the adaptive immune system to recognize a vast array of pathogens.

Other enzymes mentioned, such as DNA polymerase, RNA polymerase, and adenylate cyclase, do not specifically facilitate the addition of nucleotides at the junctions of rearranging gene segments in the context of junctional diversity. DNA polymerase primarily synthesizes new DNA strands using existing templates during DNA replication and repair, while RNA polymerase is involved in transcribing RNA from a DNA template. Adenylate cyclase is involved in the synthesis of cyclic AMP and is not directly related to nucleotide addition in the context of