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18 Cards in this Set
- Front
- Back
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What are 3 main mechanisms that allow for Antibody Diversity?
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1. Combinatorial Diversity (VDJ Recombination / H+L chain pairing)
2. Junctional Diversity (P-addition, N-addition, exonucleotylic nibbling, D reading frame) 3. Somatic Mutation |
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What 2 processes make up combinatorial diversity?
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1. V(D)J Recombination
2. H+L Chain Pairing |
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What three segments make up the Heavy Chain Variable Region?
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1. V
2. D 3. J |
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What segments make up the Light Chain Variable Region?
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ONLY V & J (No D)
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What 2 enzymes are important for VDJ recombination?
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1. RAG Enzymes
2. NHEJ (Non-Homologous End Joining) |
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What is a RSS?
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Recombination signal sequence - splice site target by RAG
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What is 12/23 rule?
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Rule that ensure V always goes to J in V(D)J Recombination
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What 2 types of light chains can antibodies express?
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1. Kappa Light Chain
2. Lambda Light Chain |
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What are the 4 mechanisms of Junctional Diversity?
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1. P-addition (RAG)
2. N-addition (TdT) 3. Exonucleolytic nibbling 4. D segment reading frames |
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What is P-addition?
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When DNA is spliced during recombination, random DNA is added to mismatched hairpin loops to create Palindromic sequence
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What is N-addition?
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- Enzyme TdT adds nucleotides to ends of broken hairpin loop during recombination
- mechanism to increase antibody diversity |
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What is it called when NHEJ trims back broken DNA breaks in recombination?
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Exonucleotylic nibbling
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What does D in D segment stand for?
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Diversity, because through different mechanisms (reading frame shifts, deletion/inversion), adds to diversity of antibodies
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Where and When does affinity maturation / somatic hypermutation occur?
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- Occurs in the lymph node germinal center AFTER B cell has been activated
- Stimulated by T CELLS, CD40L and other factors |
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What enzyme catalyzes BOTH somatic hypermutation and isotype switching?
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AID - converts C to U
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Deficiencies in AID can cause what syndrome?
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hyper-IgM syndrome
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What are 3 possible NEGATIVE outcomes of antibody diversification mechanisms?
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1. Autoreactivity
2. non-productive rearrangements 3. chromosomal translocations |
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What is allelic exclusion?
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One B Cell only produces 1 Heavy Chain and 1 Light chain and therefore only produces 1 antibody
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