Which of the following is NOT a property of the V(D)J recombinase?
A. Recognizes specific DNA sequences flanking gene segments in the antigen receptor gene loci
B. Introduces double-stranded nicks in the DNA between recombination signal sequences and the adjacent V, D, or J coding sequences
C. Promotes joining V-to-J, D-to-J, and V-to-D
D. Repairs double-stranded DNA breaks
E. Splices out intronic sequences from primary RNA transcripts
ANS: E. The V(D)J recombinase is an enzyme complex that includes the lymphocyte-specific RAG-1 and RAG-2 proteins, as well as other more widely expressed DNA repair enzymes. This recombinase acts on DNA in the antigen receptor gene loci but does not mediate RNA splicing. The RAG-1 protein binds to recombination signal sequences (RSSs), cleaves the adjacent DNA, and promotes alignment of the different segments to be joined. Other enzymes in the complex ligate the cleaved DNA ends to form the functional gene, encoding a chain of the antigen receptor.
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