Question

Question 37 12 pts During V(D)J recombination: A. How do productive rearrangements differ from nonproductive rearrangements? (6 points) B. Would you expect to have more or fewer productive rearrangements during B and T cell development in a mouse homozygous for a null mutation in terminal deoxynucleotidyl transferase (TDT)? Explain your reasoning. (6 points)

Answer 1

A. Variability,diversity and joining ensure that each antigen receptor is unique.VDJ recombination is the process by which T cells and B cells randomly assemble different segments like variability,divrsitya and joining in order to generate unique receptors.

Productive rearrangment of one allele blocks the rearrangement of the other.Diversity results from joining of gene segmentsand by adding nucleotides to the DNA sequence .

Nonproductive rearrangement takes place as a result of recombination of gene segments if they are not in correct frame.This nonproductive rearrangement occurs when nucleotide addition or substraction disrupts the frame or when a functional protein is not produced.

B. In mice,Tdt absence promotes a window in development that provide protective immunity.The sequence of immunoglobulin gene rearrangements and the points at which nonproductive rearrangements can lead to cell loss The sequence of immunoglobulin gene rearrangements and the points at which nonproductive rearrangements can lead to cell loss. Tdt activity intervenes with development of clones and cannot make protective antibodies.

Disrupted Tdt prevents N additions at every step of T and B lymphocytepromotes the development of fetal cells like T and B with some changes of cell clones to adulthood..