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Query: UMLS:C0012872 (DNA marker)
 929 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A large Swedish family with more than 250 cases of Best's macular dystrophy has been clinically and genetically studied. The gene was traced to a couple born in central Sweden in the 17th century. Highly significant evidence for genetic linkage to DNA markers on chromosome 11q13 was detected. A lod score of 15.12 was obtained at recombination fraction 0.01 with DNA marker INT2 (also called FGF3). The retinally expressed gene ROM1, which maps to the same chromosomal region is a candidate for this genetic disease.
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PMID:The gene for Best's macular dystrophy is located at 11q13 in a Swedish family. 139 87

In the present report, we summarize studies aimed at examining the reliability of chromosome heteromorphisms in analyses of chromosome 21 nondisjunction. We used two cytogenetic approaches--fluorescent in situ hybridization (FISH) to repetitive sequences on 21p and traditional Q-banding--to distinguish chromosome 21 homologues and then compared the results of these studies with those obtained by DNA markers. Using a conservative scoring system for Q-banding and FISH heteromorphisms, we were able to specify the parental origin of trisomy in 10% of cases; in contrast, DNA marker studies were informative for parental origin in almost all cases. The results of the molecular and cytogenetic studies of parental origin concurred in all cases in which assignments were made independently using both techniques. However, in 4 of 13 cases in which the molecular studies contributed to the interpretation of the cytogenetic findings, the two results did not agree with respect to the meiotic stage of nondisjunction. A relatively high frequency of crossing-over on either the short arm or proximal long arm of chromosome 21 could explain these results and may be a mechanism leading to nondisjunction.
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PMID:Nondisjunction of chromosome 21: comparisons of cytogenetic and molecular studies of the meiotic stage and parent of origin. 146 10

In cultivated beet no useful level of resistance of the beet cyst nematode (BCN) Heterodera schachtii Schm. has been found, unlike the situation in wild species of the section Procumbentes. Stable introgression of resistance genes from the wild species into Beta vulgaris has not been achieved, but resistant monosomic additions (2n = 18 + 1), diploids of B. vulgaris with an extra alien chromosome carrying the resistance locus, have been obtained. Here we describe a new series of resistant monosomic fragment addition material of B. patellaris chromosome 1 (pat-1). We further describe the cloning of a single-copy DNA marker that specifically hybridizes with a monosomic addition fragment of approximately 8 Mb (AN5-90) carrying the BCN resistance locus. This marker and another fragment-specific, single-copy DNA marker probably flank the BCN locus on the addition fragment present in the AN5-203 material, which is approximately 19 Mb in size. Furthermore, several specific repetitive DNA markers have been isolated, one of which hybridizes to AN5-90 and also to DNA from a smaller DNA segment of Beta procumbens, present in line B883, carrying a BCN resistance locus introgressed into the B. vulgaris genome. This suggests that the specific repetitive marker is closely linked to the BCN locus.
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PMID:Isolation of DNA markers linked to a beet cyst nematode resistance locus in Beta patellaris and Beta procumbens. 146 14

Linkage analysis was carried out on 20 unselected UK families segregating for adenomatous polyposis coli (APC) using four closely linked DNA probes. Significant lod scores were obtained between APC and three markers: pi 227 (D5S37) theta = 0.16; C11p11 (D5S71) theta = 0.10; and YN5.48 (D5S81) theta = 0.00. The fourth, ECB27 (D5S98), gave low lod scores. The APC gene showed linkage with at least one of the probes used in all families, which is in agreement with previous publications. Combined lod scores are now sufficiently high to allow the use of these probes in presymptomatic diagnosis. Despite the fact that 61% of persons at risk were informative for at least one DNA marker, only 15% were informative with flanking probes. One prenatal diagnosis was performed where the initial request had been for sterilisation.
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PMID:Linkage analysis in adenomatous polyposis coli: the use of four closely linked DNA probes in 20 UK families. 132 59

Huntington disease (HD) is caused by a genetic defect distal to the anonymous DNA marker D4S10 in the terminal cytogenetic subband of the short arm of chromosome 4 (4p16.3). The effort to identify new markers linked to HD has concentrated on the use of somatic cell hybrid panels that split 4p16.3 into proximal and distal portions. Here we report two new polymorphic markers in the proximal portion of 4p16.3, distal to D4S10. Both loci, D4S126 and D4S127, are defined by cosmids isolated from a library enriched for sequences in the 4pter-4p15.1 region. Physical mapping by pulsed-field gel electrophoresis places D4S126 200 kb telomeric to D4S10, while D4S127 is located near the more distal marker D4S95. Typing of a reference pedigree for D4S126 and D4S127 and for the recently described VNTR marker D4S125 has firmly placed these loci on the existing linkage map of 4p16.3. This genetic analysis has revealed that the region immediately distal to D4S10 shows a dramatically higher rate of recombination than would be expected based on its physical size. D4S10-D4S126-D4S125 span 3.5 cM, but only 300-400 kb of DNA. Consequently, this small region accounts for most of the reported genetic distance between D4S10 and HD. By contrast, it was not possible to connect D4S127 to D4S125 by physical mapping, although they are only 0.3 cM apart. A more detailed analysis of recombination sites within the immediate vicinity of D4S10 could potentially reveal the molecular basis for this phenomenon; however, it is clear that the rate of recombination is not continuously increased with progress toward the telomere of 4p.
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PMID:Increased recombination adjacent to the Huntington disease-linked D4S10 marker. 167 83

Diagnosis of the carrier status of the fragile X [fra(X)] syndrome was made in 2 unrelated women who did not express the fragile site. Both were related to several individuals with a typical fra(X) phenotype and the marker X chromosome. A restriction fragment length polymorphism (RFLP) approach was used with probes that flank the fra(X) locus (FRAXA). The loci used for risk calculations of the fra(X) genotype were DXS98 and DXS105 on the centromeric side and a recently characterized locus, DXS304, on the telomeric side. Coincidence correction for the distances between marker loci and FRAXA was made according to the Kosambi function. The DNA marker test gave the risk for one female to be a carrier of 99.7-99.9%. In another family a female was excluded from being a carrier with a probability of greater than 99.7%. The DNA marker U6.2, defining the locus DXS304, has increased the reliability of DNA based diagnosis of carrier status for females-at-risk. It is concluded that DNA analysis can serve as a valuable complement to chromosome analysis in families informative for the more closely linked flanking markers.
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PMID:Carrier detection of the fragile X syndrome using flanking loci DXS98, DXS105, and DXS304. 167 4

Malignant melanoma has been documented to display recurring abnormalities of chromosome 6, particularly the long arm (6q). Restriction fragment length polymorphism analysis was used as a molecular genetic approach to examine loci on chromosome 6q for loss of constitutional heterozygosity (LOH). Five DNA markers that recognize restriction fragment length polymorphisms along 6q and one polymorphic DNA marker for 6p were used to screen 20 autologous pairs of tumor DNA and normal DNA to determine the tumor and constitutional genotypes of each patient. LOH on chromosome 6q was identified at 21 of 53 informative loci (40%). Five patients with more than one informative locus had allele losses consistent with the loss of the entire long arm (or of an entire copy) of chromosome 6, while four other patients demonstrated terminal deletions of 6q. The chromosomal region bearing the highest frequency of 6q allelic loss (60%) is defined by the marker loci c-MYB and ESR (6q22-23 and 6q24-27). In contrast to the frequency of 6q loss, LOH was observed at loci on four other chromosomes (1, 11, 16, 17) in only 5% of cases. These results have led us to conclude that the loss of sequences from the long arm of chromosome 6 is a nonrandom and possibly biologically relevant event in human malignant melanoma.
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PMID:Loss of heterozygosity for loci on the long arm of chromosome 6 in human malignant melanoma. 168 May 51

The ret proto-oncogene has been mapped to 10q11.2 near the MEN2A locus by in situ hybridization. We carried out a linkage study of Japanese multiple endocrine neoplasia type 2A (MEN2A) families using a cosmid clone containing the ret proto-oncogene as probe. Two polymorphic alleles (A1 and A2) could be detected by digesting DNA with EcoRI: allele A1 was detected as a 10 kb fragment and A2 as 5.4 and 4.6 kb fragments. Of 11 Japanese MEN2A families analysed, four were informative, and the maximum lod score was 4.23 at a recombination fraction of 0.00. This result suggests the ret proto-oncogene to be close to the MEN2A gene and therefore possibly to be a useful DNA marker for cloning the latter.
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PMID:Tight linkage of the ret proto-oncogene with the multiple endocrine neoplasia type 2A locus. 168 18

The search for the Huntington's disease (HD) gene has prompted construction of a complete long-range restriction map of a 2.5-Mb candidate region, distal to the DNA marker D4S10. To facilitate the procurement of cloned DNA from this candidate region, we have augmented the existing regional mapping panel of somatic cell hybrids with hybrid HHW1071 containing a t(4p16;12) chromosome from a patient with Wolf-Hirschhorn syndrome. This translocation maps between D4S180 and D4S127, subdividing the HD candidate region and setting a proximal limit to the Wolf-Hirschhorn syndrome region. Using the expanded mapping panel, we have regionally assigned 14 independently cloned cosmids, five proximal to the t(4;12) breakpoint in the same region as D4S10 and nine distal to the breakpoint. By a combination of overlap with previously mapped cosmids and pulsed-field gel analysis, each of these cosmids has been positioned on the long-range restriction map of 4p16.3, increasing the clone coverage of the candidate region to approximately 40%. Single-copy probes from mapped cosmids were used to identify eight new DNA polymorphisms spanning the HD candidate region. These new DNA markers should prove valuable for analysis of recombination and linkage disequilibrium in HD, as well as for preclinical diagnosis of the disorder.
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PMID:New DNA markers in the Huntington's disease gene candidate region. 168 79

The polymorphic DNA marker D20S14 was previously mapped to human chromosome 20 and shown to be linked to two other DNA markers, D20S5 and D20S6, located at 20p12. This segment has been implicated in several human diseases. Because of its importance, we mapped the D20S14 locus to 20p12----p11.2 by radioactive in situ hybridization.
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PMID:The polymorphic DNA sequence D20S14 is assigned to human chromosome 20p12----p11.2 by in situ hybridization. 173 66


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