Meiotic evidence in Down's syndrome for 21/21 chromosome translocation or isochromosome

Down Syndrome and Recurrent Abortions Resulting from Robertsonian Translocation 21q21q

“…In the years prior to banding, it was not possible to know if the G group chromosome was a 21 or 22, so precise information is available in only a small number of families. Hecht 2 provided meiotic evidence that a 21/G translocation was 21/21, commenting that previous evidence was purely statistical. Banding has, of course, made the distinctions secure.…”

Meiotic and synaptonemal complex studies in a 14/21 translocation carrier

“…However, although the number of meiotic studies in translocation camers has been considerable (Kjessler 1966;Hecht et al 1970;Chandley et al 1972;Luciani et al 1972;Laurent et al 1973;Hultkn 1973;Koulischer & Schoysman 1974) no data are available on the pairing geometry of the multivalents, and no synaptonemal complex studies have ever been carried out in these patients. This lack of information is important because, according to recent animal data (Moses et al 1979;Elder 8c Pathak 1980) the risk of non-disjunction may vary considerably depending on the pairing characteristics of the chromosomes at meiosis.…”