Integration of 30 CA-repeat markers into the cytogenetic, genetic and YAC maps of human chromosome 21.

Abstract

The number of polymorphic DNA markers developed for the whole human genome during the last 2 years has been vastly increased. For this reason, the genetic map is continuously improving, but the cytogenetic and physical maps are not progressing at the same speed. Therefore, there is a need to integrate genetic, cytogenetic and physical mapping data. We have developed and localized on the breakpoint map of human chromosome 21 thirty microsatellite markers. Twenty of them have been used in the construction of a genetic map of chromosome 21, which contains a total of 44 markers. This map has 39 uniquely placed loci at 23 anchor points, ordered with odds of at least 1,000:1. The sex average length of the map is 64.4 cM, with the male and female lengths being 49.4 and 79.2 cM, respectively. Twenty-six of these newly developed markers have been localised on the CEPH/Généthon and Joint YAC Screening Effort YACs. Although these microsatellites were found uniformly spread along chromosome 21, the detection of various markers in the same or adjacent YACs suggests that CA-repeat microsatellites are clustered in several regions. The localization of these markers on the cytogenetic, genetic and YAC maps has provided a refined location for them and is a step further towards the construction of an integrated map of HC21.