Distinguish between coding diversity and junctional diversit

Distinguish between coding diversity and junctional diversity for immunoglobulins. What are two types of junctional diversity?

Solution

Ans.) Difference between coding diversity and junctional diversity for immunoglobulins -

Junctional diversity is the variation in the DNA sequence that is incorporated by the inappropriate joining of gene segments during the process of VDJ recombination. This process of VDJ recombination has a very significant roles for the vertebrate immune system, as it is capable of generating a huge repertoire of different T-cell receptor and immunoglobulin molecules which are required for pathogen antigen recognition by T-cells and B cells, respectively. The imprecision of joining provided by junctional diversity is expected to triple the diversity initially generated by these VDJ recombinations.

Hence junctional diversity is basically the variation in DNA sequence whereas coding diversity is the different combinations of gene segments that can be used in different rearrangement events.

On the basis of the proteins involved in the process, there is two types of junctional diversity is P and N nucleotide.

Generation of junctional diversity generation begins with the proteins, recombination activating gene-1 and -2 (RAG1 and RAG2), in combination with DNA repair proteins, such as Artemis. These proteins are responsible for single-stranded cleavage of the hairpin loops and adding a series of palindromic, P nucleotides. Succeeding to this, the enzyme terminal deoxynucleotidyl transferase (TdT), also add random N nucleotides.