a1 MRC Clinical and Population Cytogenetics Unit, Western General Hospital, Crewe Road South, Edinburgh, EH4 2XU
Cytogenetic studies have ascertained that the segregation of the X-chromosome, during the first meiotic division of the oocyte in XO mice, occurs at random, contrary to the finding of some earlier authors. The ratio of nullo-X to X-bearing oocytes at ovulation does not change with maternal age. The usefulness of the XO mouse as a model for aneuploidy production in women (Lyon & Hawker, 1973) is discussed.
(Received August 26 1982)