No abstract

receptive intercourse had been carried out in the previous two years, needle sharing in the previous five years, and frequency of douching before anal inter¬ course).1 The results indicated signifi¬ cant independent associations between both syphilis (odds ratio = 2-64; F<-001) and race (odds ratio = 2-61; P = -05) and HIV infection. The interaction term for syphilis and race was not significant (P = -31). Thus, Mr Potterat's hypothe¬ sis that syphilis is associated with HIV infection is supported by these data, but other factors must also contribute to the differences in HIV infection rates between blacks and whites.

No abstract

Break points of structural rearrangements of human chromosomes can be identified by banding techniques. The present study attempts to analyze the randomness and the distribution of the reported spontaneous break points in the human genome. Reports of break points in structural rearrangements of human chromosomes from the published sources up to October 1976 were analyzed. Based on the assumption that each unit length of band has an equal chance of being broken, χ² tests show that positions of breakage are highly non-random; that is, breaks are more frequent in the negative band areas and in the centromeric and terminal regions. In double-break rearrangements the same band types tend to rejoin. The distribution of breaks is not proportional to the chromosome length. The longer chromosomes (i.e., 1–12, X) have a lower number of breaks per unit length, while the shorter chromosomes (i.e., 13–22, Y) have a greater number of breaks per unit length with the exception of chromosomes 4, 9,10,16,17,19,20 and X. Out of the whole genome, chromosomes 9, 13, 18, 21, 22 and Y have the most breaks per unit length and chromosomes 16, 6, 2, 3 and 19 have the fewest. 18p11,21q22 and Yp11 are the three bands with most frequent breaks. There are 53 bands where no breaks have been reported.