Xg groups and sex abnormalities in people of northern European ancestry.

This paper presents a succession of tables with little comment.We are from time to time asked for the latest Xg score in certain categories of sex chromosome abnormalities and so hope some of the tables may be useful.The X-linked Xg blood group system was re- cognized late in 1961 (Mann et al, 1962).An account of its application, in the Blood Group Unit, to certain sex chromosome abnormalities in people of northern European extraction from that time until the end of April 1968 was given in the British Medical Bulletin (Race and Sanger, 1969).This present paper brings our account up to 7 January 1971, and includes some conditions not summarized in the 1969 account.Many of the cases out of which the tables are built have been published, so the present list should not be pooled with any previous publication in which the Xg groups were done by the Blood Group Unit.Xg Frequencies We have used as a standard the frequencies given by Noades et al (1966) which were based on a series of 3418 unrelated people of northem European extraction tested in the Unit: Alleles Phenotypes Males Females Xga 0 659 Xg(a+) 0.659 0-884 Xg 0-341 Xg(a -) 0-341 0-116 A more recent count (Sanger, Tippett, and Gavin, 1971) brings the total up to 6784 with, curiously and conveniently, exactly the same allele frequencies to three figures. NotationWe apologize for using the old notation XXY rather than 47,XXY and XO rather than 45,X: just