Final answer:
Recombination signal sequences (RSSs) guide DNA recombinase in pairing V and J segments during somatic recombination at a light-chain locus. The correct pairing is ensured by the presence of complementary RSSs (12/23 base pair spacers) flanking the V and J segments.
Step-by-step explanation:
The question is asking to identify the correct pairing of recombination signal sequences (RSSs) during somatic recombination at a light-chain locus. In B-cell maturation, DNA recombinase facilitates the genetic rearrangement by randomly excising most of the V (variable) and J (joining) segments of the light chain gene in germ-line B cells. A correct pairing of RSSs ensures that one V segment is joined to one J segment, thereby creating a diverse antibody repertoire.
During this recombination, RSSs, which flank the V and J segments, guide the recombination process. RSSs come in two forms, 12/23 base pair spacers, and only segments flanked by complementary RSSs (one 12 and one 23) can effectively recombine. This specificity in recombination is crucial for generating the variety of antibodies needed for the immune system to recognize a wide range of antigens.