The immunoglobulin λ variable light-chain region in Primates has been shaped by multiple, independent, small-scale and large-scale insertion/deletion events

We analyzed genomes of nonhuman primates to determine the ancestral state of a 9.1-kb insertion/deletion polymorphism, located on human chromosome 22. The 9. 1 -kb(+) allele was found in 16 chimpanzees, 3 bonobos, and 2 Bornean orangutans; however, 9 chimpanzees and 6 Sumatran orangutans showed neither the 9. 1 -kb(+) nor the 9. 1 -kb(-) allele, but a novel allele, termed 9. 1 -kb(null). A clone from a chimpanzee BAC library carrying the 9.1-kb(null) allele was sequenced: the BAC DNA aligns with the human chromosome 22 reference sequence except for a 75-kb region, suggesting that the 9. 1 -kb(null) allele originated from a deletion. Furthermore, the 9.1-kb(+) chromosomes of chimpanzees and bonobos contain a 1030-nucleotide sequence, absent in humans, that may result from a retro-transposition insertion in their common ancestor. Our results provide additional evidence that human chromosome 22 has undergone multiple small-scale and large-scale insertions and deletions since sharing a common ancestor with other primates.