Generation of Antibody Diversity Flashcards
what is V(D)J recombination?
process of DNA recombination that contributes to the immense diversity of antibody and T cell receptors
why are recombination-activating genes 1 and 2 (RAG1 and RAG2) important?
components of V(D)J recombination in developing B and T cells: cannot make B or T cells without
true/false: the generation of diversity of antigen-specific receptors on both B and T cells has many common features
true
what genes are rearranged in V(D)J recombination?
Ig for B cells
TCR for T cells
what are the two major domains in an antibody light chain?
variable region and constant region
what codes for the variable region in the light chain?
variable (V) segment
joining (J) segment
what enzyme mediates the rearrangement of receptor genes?
V(D)J recombinase
what gene segments code for the heavy chain?
variable (V) segment
diversity (D) segment
joining (J) segment
does the heavy chain have one or multiple genes coding for the constant region?
multiple
what constant region genes in the heavy chain can be expressed in the primary transcript?
mu and delta
mu leads to IgM polypeptides
delta leads to IgD polypeptides
what is germ line diversity?
an individual has multiple different V, D, and J gene segments, and multiple alleles for each exist in the population
what is combinatorial diversity?
V, D, J combinations in heavy chain rearrangement
different combinations of heavy and light chains
what is junctional diversity?
randomly added and subtracted nucleotides from joining segments
when does somatic hypermutation occur?
after antigenic stimulation of the B cells
in what species is gene conversion the major mechanism of antibody diversification?
chicken, rabbit, cattle, and sheep
do the IgM and IgD on a mature B cell have identical antigen specificities?
yes- their variable regions are exactly the same and are both produced on the primary B cell
true/false: in chickens, somatic hypermutation is the principal mechanism to create antibody diversity in B cells developing in the bursa of Fabricius
false
what is class switch recombination?
after a B cell is exposed to an antigen, it can switch to produce different classes of antibody molecules: IgG, IgE, IgA, still retain same antigen specificity
what is class switching dependent on?
antigenic stimulation
cytokines released by T cells
true/false: a naive B cell expresses both IgM and IgD as a result of class switch recombination
false: alternative splicing of RNA leads to both IgM and IgD on the naive B cell
class switching is DNA
is class switching for heavy chains, light chains, or both?
heavy chains
after class switching, how many classes can a B cell express?
one antibody class
true/false: a memory B cell can express IgG, IgA, or IgE on its surface
true
true/false: the VL domain of Ig light chain forms as a result of VDJ recombination
false: only VJ
true/false: gene conversion in B cells occurs in lymph nodes
false: only in chickens, sheep, rabbit, cattle, in primary lymphoid organs
what does the leader sequence in the variable light chain gene segment code for (also heavy chain)?
signal peptide that targets the translated polypeptide to the membrane of the cell
