The Dombrock system: linkage relations with other blood group loci.

The recognition of the blood group system called Dombrock was reported in 1965 by Swanson and her colleagues. In 1967 Tippett gave an account of the genetics of the system which included an analysis of the linkage relations of the Do locus to other blood group loci, based on families tested in the MRC Blood Group Unit up to April 1966. The present account brings the linkage analysis up to the end of May 1972. As before, the calculations were by the method of Morton (1955) as instructed by Maynard Smith, Penrose, and Smith (1961). The earlier series of families served to exclude close linkage between Do and any of the other loci but in certain comparisons the lod scores were positive for recombination fractions ranging from 0-2 upwards, as may be seen in the Appendix and the Table. These positive scores were small but left open the possibility that a linkage might ultimately be detectable. The addition of the present series of families has reduced the possibility of linkage of Do with Rh and with Fy (Appendix) but increased the evidence for linkage between Do and MNSs (Table). The antilogs of the total Do:MNSs lod scores in the Table, plotted in Fig. 1, show the relative probabilities of the recombination fractions when the scoring was through males, through females, and through either parent. That the slight evidence of linkage between Do and MNSs is given when scored through doubly heterozygous females as well as males may be a warning that chance rather than linkage may be responsible for our results. The increased recombination rate in the human female, recognized by Cook (1964/1965) and by Renwick and Schulze (1964/1965), has now been observed in several linkages. If 6' for the male were indeed about 0 33 as hinted by our data (Fig. 1) then the females would not be expected to give any indication of linkage. However, as Cook and his colleagues