Gene conversion and polymorphism: Generation of mouse immunoglobulin γ2a chain alleles by differential gene conversion by γ2b chain gene

• Published in: Cell Vol. 32; no. 2; pp. 515 - 523
• Main Authors: Ollo, Roger, Rougeon, Frangois
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 1983
• ISSN: 0092-8674; 1097-4172
• DOI: 10.1016/0092-8674(83)90471-3

We have determined the complete nucleotide sequence of the C57BL/6 allele of the mouse immunoglobulin γ2a chain gene. A comparison with the BALB/c γ2a gene for 1912 nucleotides reveals that the two alleles exhibit extensive divergence, since there are 138 single-base-pair differences and 8 insertions or deletions. We have compared the two γ2a alleles with the two corresponding γ2b alleles, which differ in only 12 positions. It appears that among the 134 differences between the two γ2a alleles, 70 are at positions where γ2a and γ2b are identical in the BALB/c haplotype and 54 are at positions where γ2a and γ2b are identical in the C57BL/6 haplotype. All these results suggest that nonreciprocal gene conversion between nonallelic genes can introduce sequence homogeneity in linked genes and can generate extensive divergence and polymorphism in allelic genes. We suggest that the γ2a and γ2b gene ancestors freely diverged after duplication, and that the conversion events were promoted by a deletion shortening the distance between the two loci.