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Two large Italian pedigrees with HLA-linked spinocerebellar ataxia (SCA1) were typed for HLA-A, -B and -DR as well as for markers either distal (F13A, D6S8) or proximal (D6S29, GLO1) to HLA. Pairwise linkage analyses of SCA1 vs. HLA-A, -B, and -DR showed peak lodscores of 5.3, 5.6 and 3.3 respectively at 7% recombination. Negative lodscores significantly excluded linkage with F13A at less than 5% and with GLO1 at less than 10%. The lodscores with D6S8 and D6S29 had only low peaks. Recombination events in the two pedigrees and the estimated genetic distances of SCA1 from GLO1 and HLA favour the hypothesis of a SCA1 location distal to both of them. An order cen-GLO1-HLA-SCA1-tel appears therefore most likely with present data. These results are discussed in relation to previous reports placing SCA1 distal to HLA in two families and

Six new Y-specific probes have been isolated and are reported. Along with another six already described they have been used in a systemic search for male specific RFLPs. An overall number of 46515 nucleotides have been screened with 12 enzymes and no polymorphic pattern observed. Our data reveal a greatly reduced level of polymorphism compared with other chromosomes.

The electrophoretic patterns of human red cell phosphoglucomutase (PGM) were determined by standard starch-gel electrophoresis on two aliquots of haemolysate, one of which was previously heat-treated. Samples from 67 families and 417 unrelated healthy subjects were examined. Heat denaturation studies combined with electrophoresis showed a greater heterogeneity of phosphoglucomutase-1 (PGM1) isozymes than that revealed by electrophoresis alone. Both PGM11 and the PGM21 isozymes turned out to be either heat-resistant (tr) or heat-sensitive (ts) and this new phenotypic property segregated along with the electrophoretic allele with which it was originally associated. Comparison of red cell PGM1 patterns of 217 PGM21-1 heterozygous individuals, analysed both as described in this paper and by acid starch-gel electrophoresis, which also distinguishes two common PGM11 (PGM1S1 and PGM1f1) and two common PGM12 (PGM2S1 and PGM2F1) allelic products, has shown that the two sets of four alleles do not coincide. Thus eight different PGM1 alleles were identified. The PGM1Str1, PGM1Sts1, PGM1Ftr1, PGM1FTSts1, PGM2Str1, PGM2Sts1, PGM2Ftr1 and PGM2Fts1 gene frequencies were estimated as 0 . 523, 0 . 066, 0 . 099, 0 . 029, 0 . 224, 0 . 012, 0 . 043, 0 . 004, respectively. Three polymorphic sites are hypothesized within the PGM1 structural gene and the observed frequencies of the eight alleles discussed in terms of 'disequilibrium' among these sites. This is the second example of a human enzyme isoelectrophoretic polymorphism revealed by research specifically aimed at detecting electrophoretically cryptic genetic variations. The technique used in this study appears to offer a reliable means of detecting isoelectrophoretic variants for proteins already known to be electrophoretically polymorphic.

The polymorphisms of human mitochondrial DNA were studied in about 150 Sardinians from Cagliari and 100 other Italians living in Rome, using total blood cell DNA and the following restriction enzymes: HpaI, BamHI, HaeII, MspI, AvaII and HincII. 1. Seven different new morphs have been identified, one for HaeII, four for AvaII and two for HincII. 2. 16 and 17 mtDNA types were observed in the Sardinian and Roman samples, respectively. Of these only seven were shared by both groups. The morphs BamHI-3, MspI-4 and AvaII-9 were found associated at a frequency (10.0%) much higher than expected (0.17%). 3. Sardinians can be differentiated from the other Italians for a higher frequency of both morph AvaII-1 (P less than 0.05) and type 1 (2-1-1-1-1) (P approximately less than 0.03), and for a lower intragroup heterogeneity (0.52 v. 0.61). 4. The Italian sample on the whole can also be differentiated from the Caucasian group previously examined for a lower frequency of BamHI morph 2 (P Yates less than 0.01), a higher frequency of HaeII morph 1 (P Yates less than 0.02) and for the presence at a non-negligible incidence (5 individuals out of 229) of the new type 57-2 (2-3-1-4-13-2). The data indicate that mtDNA polymorphisms have not only proved to be a useful tool in detecting differences among major human groups but they can also differentiate populations within the same major ethnic division.