Linkage analysis of the human HMG14 gene on chromosome 21 using a GT dinucleotide repeat as polymorphic marker

A (GT)n repeat in intron 4 of the functional human HMG14 gene on chromosome 21 was used as polymorphic marker to map this gene relative to the genetic linkage map of human chromosome 21. Variation in the length of the (GT)n repeat was detected by electrophoresis on polyacrylamide gels of DNA amplified by the polymerase chain reaction using primers flanking the repeat. The observed heterozygosity of this polymorphism in 40 CEPH families was 58% with six different alleles. Linkage analysis localized the HMG14 gene close to the ETS2 gene and locus D21S3 in chromosomal band 21q22.3.     

Linkage mapping of D21S171 to the distal long arm of human chromosome 21 using a polymorphic (AC)n dinucleotide repeat

Summary An (AC)_n repeat within the anonymous DNA sequence D21S171 was shown to be highly polymorphic in members of the 40 Centre d'Etude du Polymorphisme Humain (CEPH) families. Ten different alleles at this marker locus were detected by electrophoresis on polyacrylamide gels of DNA amplified by the polymerase chain reaction (PCR) using primers flanking the (AC)_n repeat. The observed heterozygosity was 66%. PCR amplification of DNA from somatic cell hybrids mapped D21S171 to human chromosome 21, and linkage analysis localized this marker close to the loci CD18, PFKL, D21S113 and D21S112 in chromosomal band 21q22.3. In CEPH family 12 a de novo allele has been observed in a maternally derived chromosome.     

Linkage mapping of highly informative DNA polymorphisms within the human interferon-alpha receptor gene on chromosome 21.

Two polymorphic loci within the interferon-alpha receptor (IFNAR) gene on human chromosome 21 have been identified and mapped by linkage analysis in 40 CEPH families. These markers are (1) a multiallelic RFLP with an observed heterozygosity of 0.72 and (2) a variable (AT3)n short sequence repeat at the poly(A) tail of an Alu sequence (AluVpA) with an observed heterozygosity of 0.83. This locus is close to D21S58 (theta = 0.02, zeta = 36.76) and D21S17 (theta = 0.02, Zeta = 21.76) with chromosomal band 21q22.1. Multipoint linkage analysis suggests the most likely locus order to be 21cen-D21S58-IFNAR-D21S17-21qter. Given its high heterozygosity, the IFNAR gene can be used as an index marker on human chromosome 21.     

D21S215 is a (GT)n polymorphic marker close to centromeric alphoid sequences on chromosome 21.

A plasmid, AWZ1, that contained a dinucleotide (GT)n repeat was identified from a chromosome 21-specific genomic library. When amplified by PCR from human genomic DNA, the repeat length was highly polymorphic between individuals; its location, D21S215, was mapped in the CEPH pedigrees by linkage analysis to the pericentromeric region of chromosome 21. It is the closest polymorphic marker to alphoid sequences on this chromosome.     

Three CA/GT repeat polymorphisms from loci D21S414 and D21S1234 on human chromosome 21

We report three new polymorphic CA repeat microsatellites (ABM-21, ABM-C37A, and ABM-C37B) in two different loci (D21S414 and D21S1234), located in bands q21 and q11.2 of human chromosome 21 (HC21) and that were isolated from a HC21 phage library (LA21NS01). Heterozygosities for ABM-21, ABM-C37A, and ABM-C37B were 0.74, 0.50, and 0.67 respectively. These three CA repeat markers should be useful in the construction of a high resolution genetic map of this region of HC21.     

Highly informative dinucleotide repeat polymorphism at the D11S29 locus on chromosome 11q23

Summary The informativeness of locus D11S29 as a genetic marker was improved by the identification of a highly polymorphic (GT)_n repeat within the locus. Ten alleles were identified in parents of 40 Centre d'Etude du Polymorphisme Humain families and the polymorphism information content (PIC) was 0.77. The increased PIC value thus enables refinement of the linkage map of 11q23.     

Identification of two highly polymorphic CA-repeats (D21S1224 and D21S1261) on human chromosome 21q22.3

Two highly polymorphic CA-repeat microsatellites (D21S1224 and D21S1261) are reported. The clones containing these CA-repeats (ABM-C60 and ABM-C29) have been isolated from a human chromosome-21-specific library (LA21NS01) and have been localised to the q22.3 band using a specific chromosome 21 somatic cell hybrid panel. Both polymorphisms showed heterozygosities of 0.83 in the unrelated reference parents from the Centre d'Etude du Polymorphisme Humain. These new markers should improve the map of the 21q22.3 region, which is believed to contain a large number of genes.     

A highly informative dinucleotide repeat polymorphism at D13S201, between RB1 and WND

A highly polymorphic CA repeat was identified at D13S201, between RB1 and WND at 13ql4.3.     

Fine mapping of a polymorphic CA repeat marker on human chromosome 19 and its use in population studies

A highly polymorphic microsatellite (CA)_n-marker (CAct685) previously isolated from human chromosome 19 cosmid library was localized near GPI in 19q13.1. For the fine localization of this marker, the hybridization with chromosome 19-specific cosmid libraries assembled in contigs was used. Polymorphism analysis of the marker in 12 populations of Russia and neighboring countries showed 14 alleles containing from 16 to 30 repeat units. Populations belonging to Indo-European, Uralic and Altaic linguistic families demonstrated a great similarity in allele frequency profiles. Differences between these populations were lower for CAct685 than for classical markers. Allele distribution of CAct685 in a Chukchi population belonging to the Chukchi-Kamchatkan linguistic family differs from those in all other populations, that may be typical for Mongoloid population or reflect an ethnic history of Chukchi as a small population. Thus use of the CAct685 marker seems to be effective for analysis of distant peoples.     

Chromosome-specific alpha satellite DNA: isolation and mapping of a polymorphic alphoid repeat from human chromosome 10

Distinct subsets of the human alpha satellite repetitive DNA family can be found in the centromeric region of each chromosome. Here we described the isolation and mapping of an alpha satellite repeat unit specific for human chromosome 10, using a somatic cell hybrid in which the only human centromere derives from chromosome 10. A hierarchical higher-order repeat unit, consisting of eight tandem approximately 171-bp alphoid monomer units, is defined by six restriction endonucleases. Under high-stringency conditions, a cloned representative of this 8-mer repeat family hybridizes to chromosome 10 only, both by Southern blot analysis of a somatic cell hybrid panel and by in situ hybridization. The probe furthermore detects a polymorphic restriction pattern of the alpha satellite array on chromosome 10. These features will make this probe a valuable genetic marker for studies of the centromeric region of chromosome 10.     

Subregional localization of the chromosome 21 loci D21S24 and D21S26 using physical mapping techniques

Summary We were able to refine the chromosomal position of two existing marker loci, using an extended chromosome 21 somatic cell hybrid panel. The locus D21S26 mapped in the region 21q11.2–q21.1, and the locus D21S24 in 21q22.1–q22.2. Physical and genetic analysis indicated that D21S26 is tightly linked to D21S13 and D21S16, two markers previously linked to familial Alzheimer's disease.