How does allelic exclusion prevent multiple heavy-chain rearrangements from occurring in pre-B cells?
A. RAG1 and RAG2 are down-regulated, and TdT activity is lost so that no additional heavy-chain rearrangements may take place.
B. RAG1 is up-regulated while RAG2 and TdT are down-regulated to prevent heavy-chain recombination on the second set of chromosomes.
C. RAG1 and RAG2 induce silencing of the second alleles for VH-DJH rearrangement.
D. TdT initiates light-chain rearrangement.
E. TdT releases a cytokine to trigger apoptosis in the pre-B cell.
Answer: A
Biology
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