Given the inherent vulnerability of gametogenesis, a...
Given the inherent vulnerability of gametogenesis, a logical starting position might have been that any potential damaging agent should be presumed guilty until proven innocent. As discussed in Chapter 23, large fractions of sperm and eggs, in the vicinities of 10%–20%, are chromosomally abnormal, due to aneuploidies or structural change acquired, for the most part, during meiosis. If this is what happens naturally, if gametogenesis is so susceptible normally, then surely would not agents known to compromise the integrity of the DNA and of the spindle apparatus (not to mention various artificial dietary and environmental exposures) compound the effect dramatically? Perhaps surprisingly, this seems not to be the case. Gametogenesis—provided the damage is not irreversible—often proceeds normally, or at any rate recovers, even in the setting of some heavy exposures, and no discernible increase in chromosomal abnormality is recorded in the subsequently born children. Nevertheless, if only on the pure grounds of what seems biologically reasonable and plausible, the question is not to be regarded as being closed. The fact that sperm chromosomes may, with certain agents, show an increased rate of cytogenetic abnormality is a more practical reason for maintaining a cautious view.
We outline the observations and conclusions relating to a number of medical conditions, cancer and otherwise, and touch on some environmental and lifestyle factors. The listing is not exhaustive.
Chapter. 6079 words.
Subjects: Clinical Genetics
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