Further examination of the production-line hypothesis in mouse foetal oocytes. II. T(14; 15)6Ca heterozygotes.
Pachytene oocytes from foetal mice heterozygous for the translocation T(14; 15)6Ca were screened for evidence of a "production-line" effect on chromosome pairing. Metaphase I oocytes from adult heterozygotes were also examined to determine whether any such effect on pahytene chromosome pairing is subsequently repeated during adult reproductive life as anticipated by the production-line hypothesis. It was found that as gestation proceeded the proportion of pachytene oocytes with a translocation quadrivalent declined and that with a trivalent and univalent correspondingly increased. That is, there was evidence of variation in pairing behaviour of the translocation at different times of gestation. In contrast, the proportions of metaphase I cells with either a quadrivalent or a trivalent plus univalent did not vary between adult females of different ages. Thus if the variation observed at pachytene was the result of a production-line effect, clearly this was not reflected in the behaviour of the translocation at metaphase I. Our observations therefore do not support the production-line hypothesis for the maternal age effect on nondisjunction.
Tease
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C
M.R.C. Radiobiology Unit, Didcot, Oxon, UK.
Fisher
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G
D000375:Aging / Q000235:genetics; D000818:Animals; D002875:Chromosomes; D005314:Embryonic and Fetal Development; D005260:Female; D006579:Heterozygote; D008540:Meiosis; D008677:Metaphase; D051379:Mice; D009865:Oocytes / Q000166:cytology*