Question

Which of the following accounts for allelic exclusion in rearrangement within the IgH locus?

A. Rearrangement only occurs on one homolog at a time, and once one homolog has successfully rearranged, the other is methylated to produce heterochromatin.
B. Rearrangement is regulated by VpreB and ?5, which are themselves only expressed at specific times during IgH rearrangement.
C. Both homologs rearrange simultaneously, undergoing multiple V-J rearrangements until a productive one occurs.
D. All of the above promote allelic exclusion in IgH.
E. Allelic exclusion does not occur in IgH.

Answer 1

The correct answer for allelic exclusion in the rearrangement within the IgH locus is A. Rearrangement only occurs on one homolog at a time, and successful rearrangement of one homolog leads to methylation and inactivation of the other allele, maintaining functional consistency in the immune system.

Step-by-step explanation:

Allelic exclusion in the rearrangement within the IgH locus refers to the process by which only one of the two alleles for the heavy chain of an immunoglobulin (antibody) in B cells is productively rearranged and expressed. The correct answer to which of the following accounts for allelic exclusion in rearrangement within the IgH locus is: A.

Rearrangement only occurs on one homolog at a time, and once one homolog has successfully rearranged, the other is methylated to produce heterochromatin.

This methylation process leads to the inactivation of the other allele, ensuring that only one allele produces a functional heavy chain, which is critical for the proper functioning of the immune system.

During B cell development, DNA recombinase randomly excises V and J segments from the immunoglobulin gene, leading to DNA rearrangement.

After mRNA splicing, a unique variable region capable of binding to a different antigen is created for each antibody. This ensures that each B cell has a unique receptor and contributes to the diversity of the B cell repertoire.

However, to maintain functional consistency, allelic exclusion prevents both alleles from rearranging simultaneously which could lead to non-functional or self-reactive antibodies.