L8 -VDJ recombination Flashcards

1
Q

what number chromosone is the heavy-chain locus

A

14

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2
Q

2 light chains

A

lambda - 22

kappa - 2

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3
Q

VDJ recombination simple:

A
  1. combinations of V + D + J regions
  2. any combination of light chain with any combination of a lambda or kappa chain
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4
Q

what is key about Rag-1 and 2 endonulceases

A

lymphocyte specific

= dont want ds breaks in normal cells

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5
Q

RSS sequnces structure

A

contains 3 components :
heptamer - 12/23 spacer - nonamer

a 12 nucleotide spacer can only bind to a 23

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6
Q

Rag-1 and Rag 2 mcehasim for cleavage at RSS

A
  1. Rag uses water as nucleophile to attack 3’ hydroxyl

= nick formed

  1. 3’ hydroxyl used to attack the 5’ end on complimentary/other strand

= phopsphodiester bond formed between the 2 strands = hairpin loop
= DNA after hairpin loop is removed

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7
Q

name of enzyme that undergoes junctional diversity/Non-homologous end joining in lymphocytes

A

TDT

= Terminal deoxynucleotidal transferase

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8
Q

mechanism of junctional diversity

A
  1. ku70/80 bind to hairpin loops
  2. artemesis recruited cleaving hairpin loop leaving palindromic sequnces

= DNA that used to be hydrogen bonded in complimentary strand is released and is now in same strand
= sequnce of C-G,T-A now reads C,T,G,A
= 3’ overhang

  1. TDT adds random nucleotides until complimentarity found

= new sequnce in between RSS sequnces

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9
Q

which loop is mainly impacted by junctional diversity

A

CDR3

codes for V-D-J segments
= lots of RSS sequnces to be cleaved by RAG
= lots of random nucleotides added in junctional diversity to resolve hairpin loops

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10
Q

where does somatic hypermutation take place

A

germinal centres of lymph node
- light zone of germinal centre = somatic

  • dark zone
    = affinity maturation with help of T follicular cells
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11
Q

somatic maturation and class switching key enzyme

A

AID

= Activation Induced Deaminase

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12
Q

how does somatic hypermutaion happen - AID + UNG

A
  1. AID causes deamination of cytosines
    = uracil bases made
  2. Normally would be repaired but overhwmling amount of AID

= acted on by UNG - Uracil-DNA glycolyase

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13
Q
A
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