Meiosis, ageing and male-female differences

Dr Jim Cummins cummins at POSSUM.MURDOCH.EDU.AU
Wed Sep 6 23:56:54 EST 1995

A local group has been discussing the question of the difference in pattern
of meiosis between male and female vertebrates.  They ask the following

>What induces the suspension of the oocyte in first meiotic prophase? Is it
>a factor present in the foetal ovary or just a set of developmental
>circumstances? Is it genetically encoded? Are there ever any cases when the
>suspension doesnt occur, and all the oocytes proceed through the first
>meiosis whilst still in the foetus? The class wondered if this would ever be
>a cause of infertility in humans.

>In response to the idea that this organisation minimises mutations, does
>this suggest that more mutations are due to spermatozoan chromosomes than
>oocyte? Are the mutated sperm more effectively weeded out than could be the
>case in females with a much smaller number of gametes?

This relates to the fact that sperm are subject to more mitotic divisions
in their life than are oocytes and therefore may contribute more to genetic
dysfunction of offspring.

Jim "Spermatology rules o~ o~ o~ o~" Cummins

Associate Professor in Veterinary Anatomy
Murdoch University, Western Australia 6150
Tel +61-9-360 2668, Fax +61-9-310 4144
E mail <cummins at>
URL <>
Windows 95?  More like  Mac OS '84

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