Structural organization and evolution of t-complex in Mus genus

Modern data on the structure and evolution of the t complex are discussed. The t complex is a series of inversions in the proximal region of murine chromosome 17; it contains a set of genes that determine its predominant transmission to the offspring of heterozygous males. Variants of structural organization of this genetic system (t haplotypes) have been found in wild populations of four species of genus Mus (M. domesticus, M. musculus, M. molossinus, and M. castaneus), but not in representatives of other, evolutionarily remote species of this genus. The so-called vertical, horizontal, and introgressive hypotheses are discussed of the origin and evolution of the t complex. Based on population genetic studies and molecular analysis a new hypothesis on the origin of the t-complex is put forward. This hypothesis is a synthesis between the vertical and horizontal models and assumes that all known t haplotypes had a common ancestral chromosome 17 carrying a proximal inversion.