The linkage relationships of marker sites on chromosomes no. 2 and 10.

Two families in which aberrations involving chromosome no. 2 had been previously used for linkage studies have been re-examined using banding techniques to identify the breakage sites. In one family a (2; 10)(q21;q24) translocation was identified in individuals previously thought to have a pericentric inversion of chromosome no. 2. In the other, a fragile secondary constriction site was localized to 2q13, and it was shown by bromodeoxy uridine incorporation that the origin of the triradial chromosome no. 2 was by isochromatid breakage and non-disjunction rather than by selective endoreduplication. The three marker sites, 2q13, 2q21 and 10q24, have been analysed for their linkage relationships with 15 informative marker loci which have not yet been assigned to chromosomes other than no. 2 or no. 10. No significant evidence for linkage with any of the loci tested was found.