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Male meiosis and gametogenesis in wild house mice (<i>Mus musculus domesticu</i><i>s</i>) from a chromosomal hybrid zone; a comparison between “simple” Robertsonian heterozygotes and homozygotes

1992; Karger Publishers; Volume: 61; Issue: 3 Linguagem: Inglês

10.1159/000133410

1424-8581

B. M. N. Wallace, Jeremy B. Searle, C.A. Everett,

Evolution and Genetic Dynamics

Wild male house mice Mus musculus domesticus were collected from the hybrid zone between the John o'Groats race (2n = 32) and the standard race (2n = 40) in northern Scotland. Meiosis in both homozygotes (2n = 32, 36, and 40) and single Robertsonian heterozygotes (2n = 33, 35, and 37) was found to be orderly. At prophase/metaphase I in heterozygotes, a trivalent was formed from the metacentric and two homologous acrocentrics. At pachytene, this trivalent usually had a single side arm at the position of the centromeres, as a result of nonhomologous pairing of the acrocentrics. This side arm persisted into diplotene. Generally only a single chiasma was formed between each acrocentric and the metacentric. Anaphase I nondisjunction frequencies were estimated as 1.5% for the homozygotes and 2.7% for the heterozygotes. The extent of germ cell death between the pachytene and round spermatid stages was 18% greater in heterozygotes than in homozygotes. Our results concur with previous studies which indicate that single Robertsonian heterozygotes in wild house mice have near-normal fertility.