Amplification and Rearrangement of DNA Sequences During the Evolutionary Divergence of t Haplotypes and Wild-Type Forms of Mouse Chromosome 17

Abstract

The most proximal portion of mouse chromosome 17 occurs in a variant form known as a t haplotyper which is present at a high frequency in wild populations of mus domesticus and mus musculus. While t haplotypes have been studied by a number of investigators over the last 50 years, it is only within the last 5 years that we have begun to appreciate the true nature of these unusual genetic elements (for a recent review, see Silver, 1986). A large body of new data from a number of laboratories indicates that all naturally occurring t haplotypes are closely related to each other with a characteristic genomic organization that differs from the wild-type organization of this chromosomal region. (The “wild-type chromosome 17” refers to the non-t-haplotype form normally found in mus domesticus or mus musculus). Within the structurally variant region that defines t haplotypes (approximately 20–30,000 kb of DNA encompassing the T locus and the entire MHC), are many normally functioning genes interspersed with a number of independent “mutant loci” that mediate the characteristic t haplotype effects on fertility and development.