A DNA fragment from the human X chromosome short arm which detects a partially homologous sequence on the Y chromosomes long arm.

An X linked human DNA fragment (named DXS31 ) which detects partially homologous sequences on the Y chromosome has been isolated. Regional localisation of the two sex linked sequences was determined using a panel of rodent-human somatic cell hybrids. The X specific sequence is located at the tip of the short arm ( Xp22 .3-pter), i.e. within or close to the region which pairs with the Y chromosome short arm at meiosis. However the Y specific sequence is located in the heterochromatic region of the long arm ( Yq11 -qter) and lies outside from the pairing region. DNAs from several XX male subjects were probed with DXS31 and in all cases a double dose of the X linked fragment was found, and the Y specific fragment was absent. DXS31 detects in chimpanzee a male-female differential pattern identical to that found in man. However results obtained in a more distantly related species, the brown lemur, suggest that the sequences detected by DXS31 in this species might be autosomally coded. The features observed with these X-Y related sequences do not fit with that expected from current hypotheses of homology between the pairing regions of the two sex chromosomes, nor with the pattern observed with other X-Y homologous sequences recently characterized. Our results suggest also that the rule of conservation of X linkage in mammals might not apply to sequences present on the tip of the X chromosome short arm, in bearing with the controversial issue of steroid sulfatase localisation in mouse.     

Regional localization of polymorphic DNA loci on the proximal long arm of the X chromosome using deletions associated with choroideremia

Summary In two unrelated families, males have been identified who suffer from choroideremia and at the same time have an interstitial deletion on the proximal long arm of the X chromosome. By high-resolution banding we have characterized the deletion chromosomes as del(X)(q21.1-q21.33) and del(X)(q21.2-q21.31) respectively. By Southern blot analysis we have mapped ten different polymorphic DNA loci relative to the position of the deletion and the choroideremia locus TCD. One probe, p31, was shown to cover one of the breakpoints of the smallest deletion. The following order of the loci was suggested by deletion mapping: cen-DXS106-DXS72-TCD-(DXYS1/DXYS23/DXYS5)-DXYS2-(DXYS12/DXS3)-(DXS17/DXS101)-Xqter.     

Highly polymorphic DNA sequences in the distal region of the long arm of human chromosome 18

Highly polymorphic repeated DNA sequences were detected at the end of the long arm of human chromosome 18 by a recombinant DNA probe containing 56 bp of human DNA (pERT25). This was shown by hybridization of pERT25 to DNA from a panel of human X rodent somatic cell hybrids, by dot blot hybridization to flow-sorted human chromosomes, and by in situ hybridization to metaphase chromosomes. The high degree of polymorphism detected by this 18q DNA fragment makes it potentially useful for various applications, including investigations into the genetics of trisomy 18 (Edwards syndrome), linkage studies, and paternity testing.     

Identification of a telomeric fragment from the right arm of chromosome III of Aspergillus nidulans

A minimum of 11 bands hybridising to an oligonucleotide complementary to the putative telomeric repeat sequence (TTAGGG)n was visible in a Southern blot of EcoRI-digested Aspergillus nidulans genomic DNA. All 11 were sensitive to BAL 31 exonuclease digestion, consistent with telomeric locations. Blots of DNA from aneuploid strains deleted for a dispensable, extreme distal region on the right arm of chromosome III lack a 1.3-kb EcoRI band, indicating that this fragment is located at or near the chromosome III right arm telomere.     

The restriction fragment length polymorphism of the DNA loci of human chromosome 7]

The results of comparative RFLP analysis in some DNA loci of chromosome 7 in the populations of different Ukrainian regions are presented. Significant differences in RFLP-genotype distributions among regional populations are found. The role of different genetical processes which take place in the populations of different regions of the Ukraine is under discussion.     

Identification of a telomeric fragment from the right arm of chromosome III of Aspergillus nidulans

The activities of pyruvate decarboxylase, alcohol dehydrogenase and certain glycosidases were measured for six species of yeast. Five of these yeasts could utilize one or more disaccharides aerobically, but not anaerobically, although all could use D-glucose anaerobically. That is, each of the five showed the Kluyver effect; but the sixth yeast, Saccharomyces cerevisiae, did not do so. When grown on a glycoside with which it gave the Kluyver effect, each yeast had much less pyruvate decarboxylase activity than when grown on D-glucose or another glycoside. There was no consistent corresponding lowering of activity of either alcohol dehydrogenase, or of the appropriate glycosidase. Hence, pyruvate decarboxylase may have a role in producing the Kluyver effect.     

Cloning a fragment from the telomere of the long arm of human chromosome 9 in a YAC vector

The construction of a yeast artificial chromosome containing a human DNA insert is reported. This molecule of about 200 kb behaves as a native yeast chromosome since it has a very high mitotic stability and is present in the yeast transformant clone at a copy number similar to that of the resident chromosomes. Hybridization with the TTAGGG sequence demonstrates that this chromosome contains human telomeric sequences. In situ hybridization of the biotin-labelled artificial chromosome to metaphase human chromosomes shows that the insert occupies a telomeric position on the long arm of chromosome 9. Since the fragment was cloned as an EcoRI insert and not as a telomere, it is situated medially to the telomeric sequences and harbours telomere-associated sequences, that have been shown to contain the TTAGGG sequence. The fragment represents the end of the genetic map of chromosome 9 and thus can be used to characterize the sequence and the structure of the chromosomal region that runs from the end of the chromosome to the first gene.     

Microdissection and microcloning of the long arm of human chromosome 7

DNA-fragments from the region of the long arm of human chromosme 7 to which the CF-locus has been mapped recently were isolated by microdissection and microcloning. We developed a new fixation procedure resulting in inserts of 1.0–7.0 kb in length with a mean value of 2.9 kb. Regional mapping of three clones on 7q was carried out by the use of different hybrid cell lines containing fragments of human chromosome 7.     

An extremely polymorphic locus on the short arm of the human X chromosome with homology to the long arm of the Y chromosome.

A genomic DNA clone named CRI-S232 reveals an array of highly polymorphic restriction fragments on the X chromosome as well as a set of non-polymorphic fragments on the Y chromosome. Every individual has multiple bands, highly variable in length, in every restriction enzyme digest tested. One set of bands is found in all males, and co-segregates with the Y chromosome in families. These sequences have been regionally localized by deletion mapping to the long arm of the Y chromosome. Segregation analysis in families shows that all of the remaining fragments co-segregate as a single locus on the X chromosome, each haplotype consisting of three or more polymorphic fragments. This locus (designated DXS278) is linked to several markers on Xp, the closest being dic56 (DXS143) at a distance of 2 cM. Although it is outside the pseudoautosomal region, the S232 X chromosome locus shows linkage to pseudoautosomal markers in female meiosis. In determining the X chromosome S232 haplotypes of 138 offspring among 19 families, we observed three non-parental haplotypes. Two were recombinant haplotypes, consistent with a cross-over among the S232-hybridizing fragments in maternal meiosis. The third was a mutant haplotype arising on a paternal X chromosome. The locus identified by CRI-S232 may therefore be a recombination and mutation hotspot.     

Isolation and regional localization of DNA segments revealing polymorphic loci from human chromosome 13.

A recombinant DNA library enriched for portions of human chromosome 13 has been constructed from a hamster-human somatic cell hybrid that contained human chromosomes 13, 12, and 6p. A total of 733 phages were identified that contain human DNA inserts, and 46 single-copy subfragments have been derived and used as probes on Southern transfers of genomic DNA isolated from unrelated individuals. From this set, nine fragments revealing polymorphic loci (RFLP) in Msp I- or Taq I-digested DNA have been identified, of which three are polymorphic with both enzymes. Six of these probes have been shown to segregate concordantly with human chromosome 13 in a somatic cell hybrid mapping panel, and the RFLPs at these loci have been shown to behave as codominant Mendelian alleles. Additionally, hybridization to DNA isolated from cells containing various deletions of chromosome 13 has allowed regional localization. This recombinant DNA library will be useful in the study of retinoblastoma as well as in the study of the mechanisms responsible for abnormalities of this autosome.     

A polymorphic locus on the long arm of chromosome 20 defined by two probes from a single cosmid

Summary Two probes from the random human cosmid c1-37 detect restriction fragment length polymorphisms in humans. The loci revealed by these probes are in linkage equilibrium and constitute a compound polymorphic locus with a polymorphism information content of 0.54. A somatic cell hybrid panel has been used to map the probes to chromosome 20; in situ hybridization studies confirm this localization and indicate that the locus is on 20q13. This is the first polymorphic locus to be assigned to the long arm of chromosome 20.     

Interstitial deletion of the long arm of chromosome 7

Summary Chromosome studies were carried out in a girl because of psychomotor retardation and difficulty in swallowing. The girl was admitted to hospital for the first time when 25 months old. The most characteristic signs revealed by the physical examination were short distal ulnar phalanges, clitoral hypertrophy, and very thin outer ear cartilages.An interstitial deletion of the long arm of chromosome 7 was observed: 7q22::7q31.Laboratory investigations revealed a remarkably high level of IgG, immunoglobulin, and an elevated value of serum FSH. No evidence of gene loci located at the deleted part of chromosome 7 were found.     

Interstitial deletion in the long arm of chromosome 7

An interstitial deletion of 7q (q31.2-q32.3) is reported. Main features of this boy included facial dysmorphy, psychomotor retardation and absence of language.     

Repeated DNA sequences in the distal long arm of the human X chromosome

Summary Two DNA probes from within a single large insert from a recombinant phage-DNA library that was constructed from flow-sorted chromosomes enriched for the human X chromosome were shown to hybridize with repeated X-specific and autosomal DNA sequences. The X-chromosomal repeated sequences were assigned to the distal long arm of the X chromosome by both hybrid mapping and in situ hybridization. Fine mapping places these repeats in a region of Xq28 between DX13 (DXS15, in distal Xq28) and factor VIII (F8C, in proximal Xq28). The location of the X-specific repeats makes them potentially useful for future investigations of discases mapping to the distal long arm of the X chromosome, such as the fragile X syndrome.     

Isolation of a new polymorphic TC maize microsatellite located on the long arm of chromosome 10

Simple sequence repeats (SSR), also called microsatellites, were previously proved to be an important class of DNA markers. The isolation, mapping and designing of primers to the flanking regions of a new maize SSR is reported. The new marker, with a core motif of (TC) 12, designated as MZETC34, was mapped to the long arm of chromosome 10.     

The human gene encoding acetylcholinesterase is located on the long arm of chromosome 7.

Acetylcholinesterase (AChE) is a secreted enzyme essential for regulating cholinergic neurotransmission at neuronal and neuromuscular synapses. In view of the altered expression of AChE in some central neurological and neuromuscular disorders with a probable genetic basis, we have identified the chromosomal location of the gene encoding AChE. Chromosomal in situ suppression hybridization analysis revealed a single gene to be at 7q22, a result which was confirmed by PCR analysis of genomic DNA from a human/hamster somatic cell hybrid containing a single human chromosome 7. The AChE gene thus maps to the same region in which frequent nonrandom chromosome 7 deletions occur in leukemias of myeloid cell precursors known to express the enzyme during normal differentiation.     

Kinetics of DNA replication in a dicentric X chromosome formed by long arm to long arm fusion

Summary Utilizing the 5-bromo-deoxyuridine (BrdU) incorporation technique, we have recently studied the DNA replication kinetics in a dicentric X chromosome, formed by long arm-to-long arm fusion at band q23, from a 16-year-old black female with primary amenorrhea. The patient has a karyotype 45,X/46,X,dic(X)(q23).In the buccal smear the presence of X chromatin was found in 33% of the cells examined. The Barr bodies are large and 21% of them are bipartite. DNA replication studies were performed on the patient's lymphocytes by the thymidine pulse (T-pulse) method and confirmed comparatively by the BrdU pulse (B-pulse) method. The results indicate that the dicentric X chromosome is always late-replicating. The replication pattern is symmetric on both sides of the breakpoint and the replication sequence is, in order, p11, p22, q1(1–3), q22, q23, p21, and q21. This finding is comparable to those of other investigators and supports the theory that there exist two inactivation centers in the dicentric X chromosome, located on or near the q21 band.     

Radiation hybrid map of 13 loci on the long arm of chromosome 5.

Radiation hybrid mapping was used in conjunction with a natural deletion mapping panel to predict the order of and distance between 13 loci in the distal portion of the long arm of human chromosome 5. A panel of irradiation hybrids containing fragments of 5q was generated from an HPRT+ Chinese hamster-human cell hybrid containing a derivative chromosome 5 [der(5)t(4;5)(5qter----5p15.1::4p15.1----4pter)] as its only human DNA. One hundred nine radiation hybrids containing human DNA were screened with polymerase chain reaction primer sets representing nine genes encoding growth factors, growth factor receptors, or hormone receptors (IL3, IL4, IL5, CSF1R, FGFA, ADRB2, GRL, GABRA1, and DRD1) as well as four other loci (FER, SPARC, RPS14, and CD14) to generate a radiation hybrid map of the area 5q21-q35. A physical map predicting the order of and distance between the 13 loci was constructed based on segregation of the 13 loci in hybrid clones. The radiation hybrid panel will be useful as a mapping tool for determining the location and order of other genes and polymorphic loci in this region as well as for generating new DNA probes from specific regions.