[Increased risk of tisomy 21 in offspring of carriers of balanced non-contributing autosomal rearrangements is not explained by interchromosomal effect].

Only relatively recently the suggestion that interchromosomal effect (ICE) may be present in man had stopped to be argued. At once it became evident that this phenomenon is inherent to a proportion of balanced chromosome rearrangement carriers, predominantly to patients with fertility problems. It is important to establish whether ICE operates in genome of fertile rearrangement carriers and to determine what kind of rearrangement and how far increases a risk of aneuploidy offspring. Using own and literature data 1) we have assessed rates of inherited non-contributing balanced rearrangements in patients with trisomy 21 (T21) and rates of both mutant and inherited non-contributing balanced rearrangements in parents of offspring with T21 and 2) we have analyzed a parental origin of T21 in affected offspring of carriers of balanced rearrangement. We have found that carriers of balanced reciprocal translocation or inversion, but not robertsonian translocation, are at increased risk of T21 offspring. However these data do not support the existence of ICE in its common sense, i.e. as an effect of rearrangement on other chromosome's segregation at the carrier's meiosis. Probably the data obtained suggest an effect of paternal rearrangements on maternal chromosomes segregation after fertilization.