TRANSLOCATION of Down's syndrome usually involves chromosomes in groups D (13-15) and group G (21-22). Although it only accounts for about 3% to 4% of all cases of Down's syndrome and is sporadic in most cases, it is important because it may be inherited from phenotypically normal carriers. The recurrence risk in such families is high.1 However, there seems to be differences in the risk, depending on who is the carrier of the translocated chromosome. If the mother is a carrier of a D/G translocation chromosome, the chances are a little more than one in three of having a normal child, a little more than one in three of having a phenotypically normal translocation carrier, and between one in three and one in ten of having a child with Down's syndrome.2 If the father is the D/G translocation carrier, then the risk of a child with Down's syndrome
PORTER IH, BROWN CD, MELE D. Paternal Transmission of a D/G Translocation of Down's Syndrome. Am J Dis Child. 1966;112(3):260–261. doi:10.1001/archpedi.1966.02090120128016
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