This paper describes the Centre d'Etude du Polymorphisme Humain (CEPH) consortium linkage map of chromosome 9. A total of 124 markers were typed in the CEPH family DNAs by 14 contributing laboratories; of these, 42 loci are ordered on the map with likelihood support of at least 1000:1. The uniquely placed markers include 31 that can be typed by PCR. A further 28 markers that can be typed by PCR are approximately positioned on the map. Multilocus linkage analysis with CR1-MAP has produced male, female, and sex-averaged maps extending for 176, 237, and 209 cM, respectively, while sex-averaged maps produced with MAPMAKER and the multiple two-point program MAP extended for 170 and 129 cM, respectively. The male map contains only two intervals greater than 10 cM, and the mean genetic distance between the 42 uniquely placed loci is 4.3 cM. However, no markers were available to anchor the map at either telomere or the centromere. The results confirm the high level of interference suggested by chiasma maps of chromosome 9. Detailed meiotic breakpoints for three of the families are shown. These can be used to provide rapid placement of any new marker without the need for statistical analysis.
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