"Major minisatellite loci" detected by minisatellite clones 33.6 and 33.15 correspond to the cognate loci D1S111 and D7S437

G. Chimini et al. (1989, Genomics 5: 316-324) have recently reported that the two multilocus DNA fingerprinting probes 33.6 and 33.15 each detect a single major site in the human genome, at 1q23 and 7q35-q36, respectively, and speculate that these sites represent particularly large loci homologous to these probes. However, the human minisatellite loci cloned in 33.6 and 33.15 can themselves be assigned by somatic cell hybrid analysis to 1cen-q24 and 7q31.3-qter, respectively, corresponding to the "major loci" of Chimini et al. Furthermore, under their hybridization conditions, both 33.6 and 33.15 act largely as locus-specific minisatellite probes. The "major minisatellite loci" postulated by Chimini et al. do not therefore appear to represent major localized clusters of minisatellites in the human genome, but rather the loci cloned in 33.6 and 33.15.     

Analysis of the VNTR locus D1S80 by the PCR followed by high-resolution PAGE.

Allelic data for the D1S80 locus was obtained by using the PCR and subsequent analysis with a high-resolution, horizontal PAGE technique and silver staining. Compared with RFLP analysis of VNTR loci by Southern blotting, the approach described in this paper offers certain advantages: (1) discrete allele resolution, (2) minimal measurement error, (3) correct genotyping of single-band VNTR patterns, (4) a nonisotopic assay, (5) a permanent record of the electrophoretic separation, and (6) reduced assay time. In a sample of 99 unrelated Caucasians, the D1S80 locus demonstrated a heterozygosity of 80.8% with 37 phenotypes and 16 alleles. The distribution of genotypes is in agreement with expected values according to the Hardy-Weinberg equilibrium. Furthermore, the observed number of alleles and the level of heterozygosity, obtained through the protocol described here, were congruent with each other in accordance with the expectation of a mutation-drift equilibrium model for a single, homogeneous, random-mating population. Therefore, the analysis of D1S80 and similar VNTR loci by amplified fragment length polymorphism (AMP-FLP) may prove useful as models for population genetic issues for VNTR loci analyzed by RFLP typing via Southern blotting.     

Human dopamine transporter gene (DAT1) maps to chromosome 5p15.3 and displays a VNTR.

The human dopamine transporter (DAT1) gene is localized to chromosome 5p15.3 by in situ hybridization and PCR amplification of rodent somatic cell hybrid DNA. Analysis of a 40-bp repeat in the 3' untranslated region of the message revealed variable numbers of the repeat ranging from 3 to 11 copies. These results will aid in the investigation of a role for this gene in genetic disorders of the dopaminergic system in humans.     

Characterization of three VNTR systems at D21S112.

D21S112 is a highly polymorphic marker on the long arm of chromosome 21. Our analysis of this locus indicated the presence of three VNTR systems. We estimated the heterozygosity of each system and sequenced one of the repetitive regions. Utilizing PCR, we demonstrated that the sequenced VNTR is responsible for the system with the highest level of heterozygosity. Combining data from the three systems makes D21S112 one of the most informative loci on the chromosome.     

Sequences homologous to the human D1S1 locus present on human chromosome 3.

We have investigated the segregation, in somatic cell hybrids, of the human D1S1 locus, previously assigned to 1p36 by in situ hybridization. We have shown that the clone which defines this locus, lambda Ch4A-H3, originates from human chromosome 3, but contains a 1.7-kilobase (kb) PstI-HindIII repetitive element that is also present on chromosome 1, probably distal to PGD. The clone recognizes restriction fragment length polymorphisms within the single-copy sequence on chromosome 3 and one for the enzyme StuI in the repeated sequence on chromosome 1. These experiments thus expose a level of complexity in the D1S1 locus not revealed by earlier in situ hybridization studies.