TRISOMY-21 (DOWN SYNDROME) - STUDYING NONDISJUNCTION AND MEIOTIC RECOMBINATION BY USING CYTOGENETIC AND MOLECULAR POLYMORPHISMS THAT SPAN CHROMOSOME-21

  • 1 February 1988
    • journal article
    • research article
    • Vol. 42  (2) , 227-236
Abstract
By combining molecular and cytogenetic techniques, we demonstrated the feasibility and desirability of a comprehensive approach to analysis of nondisjunction for chromosome 21. We analyzed the parental origin and stage of meiotic errors resulting in trisomy 21 in each of five families by successfully using cytogenetic heteromorphisms and DNA polymorphisms. The 16 DNA fragments used to detect polymorphisms spanned the length of the long arm and detected recombinational events on nondisjoined chromosomes in both material meiosis I and material meiosis II errors. The meiotic stage at which errors occurred was determined by sandwiching the centrometere between cytogenetic heteromorphisms on 21p and an informative haplotype constructed using two polymorphic DNA probes that map to 21q just below the centromere. This study illustrates the necessity of combining cytogenetic polymorphisms on 21p with DNA polymorphisms spanning 21q to determine (1) the source and stage of meiotic errors that lead to trisomy 21 and (2) whether an association exists between nondisjunction and meiotic recombination.