Lack of evidence for association of meiotic nondisjunction with particular DNA haplotypes on chromosome 21.

The hypothesis of a predisposition to meiotic nondisjunction for chromosome 21 carrying a specific molecular haplotype has been tested. The haplotype in question is defined by the restriction fragment length polymorphisms for the D21S1/D21S11 loci. Our results obtained on a sample of Northern Italian families with the occurrence of trisomy 21 (Down syndrome) failed to support this hypothesis, contradicting a previous study [Antonarakis, S. E., Kittur, S. D., Metaxotou, C., Watkins, P. C. & Patel, A. S. (1985) Proc. Natl. Acad. Sci. USA 82, 3360-3364]. These findings rule out an association between any specific D21S1/D21S11 haplotype (as well as other haplotypes for the D21S13, ETS2, and D21S23 loci) and a putative cis-acting genetic element favoring the meiotic missegregation of chromosome 21. For this reason, no preventive screening for couples at risk for trisomy 21 may be based on any of the haplotypes tested.