Breakout Session 2 Flashcards
Three sources of Immunoglobulin Diversity in B cells?
1)Combinatorial Diversity (Somatic Recombination)
2) Junctional Diversity
3) Mutational Diversity (Somatic Hypermutation)
What type of diversity is achieved during B cell development via random
recombination of different variable gene sequences (e.g molecular
shuffling or somatic recombination) to encode novel variable regions for both the heavy/light chains.
Combinatorial diversity
___chains: recombination of V, D, and J heavy chain regions to encode a variable region
____: recombination of V and J light chain genes to encode the variable
region
Heavy Chains
Light Chains
True or False: Each gene locus undergoes an independent V(D)J recombination to
rearrange DNA
True
What order is found in heavy chain? light?
Heavy: V to D to J
Light: V to J
Each V, D, and J segment is surrounded on both sides by conserved non-coding
recombination sequences that direct the enzymes involved in V(D)J recombination
to that specific region of the DNA. What are these segments known as?
Recombination Signal Sequences (RSS)
The RSS is composed of what three sequences?
1) Heptamer sequence
2) Spacer sequence
3) Nonamer sequence
True or False: The RSS sequences are critical for making sure that the correct gene segments are
combined with one another
True
______ states that a gene segment flanked by an RSS with a 12 bp spacer can only be joined to a gene flanked by
an RSS with a 23 bp spacer
12/23 Rule
The _______ is a complex of enzymes that breaks
the DNA at the RSS sequences and catalyzes the recombination and repair of the double stranded DNA breaks
VDJ Recombinase
True or False: RAG1/RAG2 (Recombinase activating genes) are lymphoid specific genes only expressed during B and T cell
development
True
_____bind to the RSS sequences and make 2
single stranded DNA cuts just 5’ of each bound RSS
The RAG proteins
______ this protein binds the ends of double stranded DNA breaks
Ku70/80
____: this enzyme mediates DNA bending and hairpin cleavage.
Artemis
Which proteins promote and help catalyze the
repair of double-stranded DNA breaks?
DNA ligase IV and XRCC4
The double stranded break
on the excised DNA is repaired precisely to form the ____and the resulting
circular DNA is lost
signal joint
In contrast, the gene segments that are combined on the chromosome are joined imprecisely to form the _____
coding joint
_____ are the
lymphoid-specific proteins that induce the breaking of the DNA for V(D)J recombination
to occur.
RAG 1/2
The ability of B cells to undergo genetic rearrangement is limited to when ____
are expressed.
RAG1/RAG2
During the repair of the coding joint on the chromosome by VDJ recombinase, an
enzyme called ___ modifies the
chromosome to add, change, or delete nucleotides
TDT (terminal deoxynucleotidal transferase)
TDT is targeted to
the ____ by interacting with the enzymes that repair the dsDNA breaks.
coding joint
True or False: TDT enzyme modifies the nucleotides during VDJ recombination at the coding joint to
increase the diversity, by a factor of up to 3x107
True
True or False: If aberrant double stranded breaks occur in lymphocytes and, if the components of VDJ recombinase are expressed, there is the potential to repair the double stranded DNA by placing an oncogene behind a promoter that is constitutively “ON”.
True
