A cytogenetic study of 112 cases with Down's syndrome.

(Mikkelsen 1967) -3% (BrƒÓgger 1967); in patients born to mothers younger than 30 years it is 8.3%, and in those born to mothers older than 30 years it is 1.2% (Mikkelsen 1967). Between the patients born to mothers older and younger than 30 years the difference is highly statistically significant. The frequency of D/G translocations is about the same as the frequence of G/G translocations. About 41% of D/G translocations are inherited while only a small fraction of G/G translocations are transmitted from a parent (BrƒÓgger 1967). The frequency of chromosome mosaicism among patients with typical Down's syndrome is about 1% (Mikkelsen 1967). The purpose of this study was to obtain information about the frequency of translocations in our popula tion of Down's syndrome.