Breakout Session 2

Question 1

Three sources of Immunoglobulin Diversity in B cells?

Answer 1

1)Combinatorial Diversity (Somatic Recombination)

2) Junctional Diversity

3) Mutational Diversity (Somatic Hypermutation)

Question 2

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.

Answer 2

Combinatorial diversity

Question 3

___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

Answer 3

Heavy Chains

Light Chains

Question 4

True or False: Each gene locus undergoes an independent V(D)J recombination to
rearrange DNA

Answer 4

True

Question 5

What order is found in heavy chain? light?

Answer 5

Heavy: V to D to J
Light: V to J

Question 6

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?

Answer 6

Recombination Signal Sequences (RSS)

Question 7

The RSS is composed of what three sequences?

Answer 7

1) Heptamer sequence
2) Spacer sequence
3) Nonamer sequence

Question 8

True or False: The RSS sequences are critical for making sure that the correct gene segments are
combined with one another

Answer 8

True

Question 9

______ 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

Answer 9

12/23 Rule

Question 10

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

Answer 10

VDJ Recombinase

Question 11

True or False: RAG1/RAG2 (Recombinase activating genes) are lymphoid specific genes only expressed during B and T cell
development

Answer 11

True

Question 12

_____bind to the RSS sequences and make 2
single stranded DNA cuts just 5’ of each bound RSS

Answer 12

The RAG proteins

Question 13

______ this protein binds the ends of double stranded DNA breaks

Answer 13

Ku70/80

Question 14

____: this enzyme mediates DNA bending and hairpin cleavage.

Answer 14

Artemis

Question 15

Which proteins promote and help catalyze the
repair of double-stranded DNA breaks?

Answer 15

DNA ligase IV and XRCC4

Question 16

The double stranded break
on the excised DNA is repaired precisely to form the ____and the resulting
circular DNA is lost

Answer 16

signal joint

Question 17

In contrast, the gene segments that are combined on the chromosome are joined imprecisely to form the _____

Answer 17

coding joint

Question 18

_____ are the
lymphoid-specific proteins that induce the breaking of the DNA for V(D)J recombination
to occur.

Answer 18

RAG 1/2

Question 19

The ability of B cells to undergo genetic rearrangement is limited to when ____
are expressed.

Answer 19

RAG1/RAG2

Question 20

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

Answer 20

TDT (terminal deoxynucleotidal transferase)

Question 21

TDT is targeted to
the ____ by interacting with the enzymes that repair the dsDNA breaks.

Answer 21

coding joint

Question 22

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

Answer 22

True

Question 23

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”.

Answer 23

True