We isolated extrachromsomal circular DNA from the bursa of 18‐day chick embryos and cloned their BamHI fragments into a phage vector. We found examples of the signal joint fused by Vλ1‐Jλ, rearrangement and the sequences homologous to Vλ1 segments that showed: (1) clustered V pseudogene (ΨV) germ‐line segments containing new ΨV26, (2) a head‐to‐tail duplication of ΨV13‐ΨV12 region and (3) chimeric structures composed of 5′‐Vλ1 and 3′‐ΨV segments. Both intrachromosomal tandem duplications and extrachromosomal circles may be generated by unscheduled DNA synthesis and recombination. The chimeric structure of Vλ1 joined with upstream ΨV segments suggests the involvement of V gene replacement for somatic diversification of the immunoglobulin genes in addition to a mechanism of segmental gene conversion.
All Science Journal Classification (ASJC) codes
- Immunology and Allergy