The translocation heterozygote (carrier) may have a risk to have a child who would be mentally and physically abnormal due to a “segmental aneusomy.” Typically, the...
The translocation heterozygote (carrier) may have a risk to have a child who would be mentally and physically abnormal due to a “segmental aneusomy.” Typically, the imbalance is due to a segment of one of the participating chromosomes being duplicated and a segment of the other chromosome being deleted. This confers a partial trisomy and a concomitant partial monosomy. A few translocations are associated with a high risk, as much as 20%, or very rarely up to 50%, to have an abnormal child. Many translocations imply an intermediate level of risk, in the region of 5%–10%. Some carriers have a low risk, 1% or less; but the woman who is a carrier, or the partner of a male carrier, may have a high miscarriage rate. Others imply, apparently, no risk to have an abnormal child, but the likelihood of miscarriage is high. Yet others, discovered fortuitously, seem to be of no reproductive significance, with carriers having no difficulties in conceiving or carrying pregnancies and having normal children. The counselor needs to distinguish these different functional categories of translocation, in order to provide each family with tailor-made advice.
Chapter. 22727 words. Illustrated.
Subjects: Clinical Genetics
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