Showing papers on "Chromosome 21 published in 1975"

Chromosome imprinting and the mammalian X chromosome.

Abstract: Chromosome imprinting is the process by which one of two genetically homologous chromosomes is predetermined to function differently from the other at a subsequent stage in development. In the coccid insects, imprinting occurs in the egg, at the time of fertilisation; it probably occurs at the same time and site in mammals, and possibly also in Sciara.

Cytogenetic analysis of chromosome 3 in drosophila melanogaster: mapping of the proximal portion of the right arm

Abstract: In order to define more precisely the most proximal portion of chromosome 3R in Drosophila melanogaster , several new chromosome aberrations involving this region have been recovered and analyzed. These new arrangements were recovered as induced reversions of two dominant mutations, Antp Ns and dsx D , located in the region of interest. The results of the analysis have allowed the localization of several existing mutations, have further elucidated the complex homoeotic locus which resides in this region, and have confirmed the efficacy of this type of screen in the analysis of specific chromosome regions.

Familial Down syndrome due to t(10;21) translocation: evidence that the Down phenotype is related to trisomy of a specific segment of chromosome 21.

Abstract: This report deals with a reciprocal t(10;21) translocation which is observed in three generations of a family. Included are examples of the balanced translocation, adjacent-2 segregation producing three patients with trisomy of the distal long arm of chromosome 21 and the Down syndrome, and 3-1 disjunction producing trisomy of the proximal segment of chromosome 21 in a mildly mentally retarded boy without phenotypic features of the Down syndrome. These data provide evidence that the Down phenotype is attributable to trisomy of the distal long arm of chromosome 21.

Human karyotype polymorphism

Abstract: In the article the results of a parallel routine and fluorescent investigation of chromosomes in 103 normal individuals (51 women and 52 men) are presented There were no gross chromosomal abnormalities in the individuals studied, but in 30 (291%) of them various autosomal variants (1q+, 9q+, 16q+, 17ph+, Dp+, Gp+, et al) were detected by the routine method Five men (95%) had Y chromosome variants The authors were successful in identifyng practically all these chromosomal variant by their fluorescent banding patterns The occurrence of brilliant fluorescent bands in chromosome parts showing variable fluorescence (paracentromeric area of chromosome 3, short arms and satellites of acrocentric chromosomes and the distal part of Y chromosome) was also investigated Some questions connected with karyotype polymorphism in man are discussed

Genetic analysis of the 5s rna genes in drosophila melanogaster

Abstract: The 5S RNA genes of Drosophila melanogaster in either an isogenic wild-type or a multiply inverted (SM1) chromosome 2 increase their multiplicity when opposite a deficiency for the 5S gene site. This is analogous to the compensation phenomenon previously described for the 18S and 28S ribosomal RNA genes of the X chromosome nucleolus organizer region. Molecular hybridization of 5S RNA to DNA containing various doses of the 56F1-9 region of chromosome 2 demonstrates that most, if not all, of the 5S genes reside in or near this region. Also, a deficiency missing approximately one-half of the wild-type number of 5S genes was isolated and genetically localized. This mutant has a phenotype like that of bobbed, a mutant known to be partially deficient in 18S and 28S ribosomal RNA genes. Finally, we report the existence of a chromosomal rearrangement which splits the second chromosome into two segments, each containing 5S DNA.

Partial trisomy for the long arms of chromosome no. 5 due to insertion and further 'aneusomie de recombinaison'.

Abstract: Five members of a family with a balanced insertion (1;5)(q32;q11q22) are presented. The daughter of one of them shows multiple malformations and a partial trisomy for the long arms of chromosome No. 5 (5q11 to 5q22 segment) resulting from a 'aneusomie de recombinaison' in her mother. The propositus' karyotype is 46,XX,rec(1;5)ins (1;5)(q32;q11q22). This case is the first reported example of an insertion between two chromosomes followed by 'aneusomie de recombinaison'. It also is the first reported case of trisomy invovling the long arms of chromosome No. 5.

Mitotic chromosome loss in a disomic haploid of Saccharomyces cerevisiae.

Abstract: Experiments designed to characterize the incidence of mitotic chromosome loss in a yeast disomic haploid were performed. The selective methods employed utilize the non-mating property of strains disomic for linkage group III and heterozygous at the mating type locus. The principal findings are: (1) The frequency of spontaneous chromosome loss in the disome is of the order 10-4 per cell; this value approximates the frequency in the same population of spontaneous mitotic exchange resulting in homozygosity at the mating type locus. (2) The recovered diploids are pure clones, and thus represent unique events in the disomic haploid. (3) Of the euploid chromosomes recovered after events leading to chromosome loss, approximately 90% retain the parental marker configuration expected from segregation alone; however, the remainder are recombinant for marker genes, and are the result of mitotic exchanges in the disome, especially in regions near the centromere. The recombinant proportion significantly exceeds that expected if chromosome loss and mitotic exchange in the disome were independent events. The data are consistent with a model proposing mitotic nondisjunction as the event responsible for chromosome loss in the disomic haploid.

Gene dosage: evidence for assignment of erythrocyte acid phosphatase locus to chromosome 2.

Abstract: A child, trisomic for the distal short arm of chromosome 2 due to a familial 2/18 translocation, has elevated levels of activity of erythrocyte acid phosphatase [orthophosphoric-monoester phosphohydrolase (acid optimum), 3.1.3.2] Ferguson-Smith et al. [(1973) Nature New Biol. 243, 271-274] previously had found decreased levels of activity and loss of expression of an erythrocyte acid phosphatase allele in a subject who lacked one of the two homologous regions containing the distal three bands of chromosome 2. They suggested that the locus for erythrocyte acid phosphatase is located on that segment. Our findings provide further evidence for this assignment and also suggest an in vivo gene dosage effect of this autosomal locus, which depends on both the type and number of alleles present.

Non-antiviral activities of interferon are not controlled by chromosome 21

Abstract: USING mouse–human cell hybrids, Tan et al.1 assigned the gene(s) for the expression of the antiviral state induced by human (leukocyte) interferon to chromosome 21; furthermore, human skin fibroblasts trisomic for chromosome 21 proved more sensitive to the antiviral activity of human (leukocyte) interferon than normal diploid fibroblasts or trisomic 18 or 13 fibroblasts2,3. Since the non-antiviral and antiviral activities of interferon remain inseparably linked through approximately a million-fold purification (ref. 4 and references cited therein), the question may be raised whether these various activities of interferon are accounted for by the same mechanisms and whether the expression of the non-antiviral activity of (human) interferon is also controlled by chromosome 21.

Heterochromatic chromosomes and satellite DNAs of Drosophila nasutoides.

Abstract: Drosophila nasutoides is distinguished from other Drosophila species in that the metaphase karyotype shows a pair of very large V-shaped chromosomes. With Giemsa, a distinctive C-banding pattern is revealed along the arms of this large chromosome, indicating a largely heterochromatic nature. Furthermore, the banding patterns of the arms are symmerical, indicating that it is an iso-chromosome. A comparison between the metaphase karyotype and polytene chromosomes suggests that the large V chromosome appears as the dot chromosome in polytene squash. One autosome has twice the arm length of typical Drosophila polytene chromosomes and arose either by centric fusion and a pericentric inversion, or by translocation connecting distal ends with a subsequent loss of one centromere. This chromosome appears to have a short arm which ectopically pairs with the proximal region of the long arm, representing a duplication of about ten bands. When the nuclear DNA is examined by neutral CsCl gradient, four satellites are observed. As much as sixty percent of the total DNA appears as satellites in the lysate of larval brains. No satellite was detectable in the lysate of salivary glands. These observations led us to suggest that the heterochromatic nature of the large V chromosome is due to the presence of all four satellites in this chromosome and that this large chromosome appears as the dot because of the under-reduplication of the satellites during polytenization.

Confirmation of the identification of the rye chromosome in 1b/1r wheat-rye chromosome substitution and translocation lines

Abstract: Chromosome 1R is readily distinguished from all other rye chromosomes and from all the chromosomes of hexaploid wheat in both Giemsa stained root-tip metaphase cells and in Feulgen stained antipoda...

Regulation of chromosome 21-directed anti-viral gene(s) as a consequence of age.

Abstract: WHEN human fibroblast cells are cultured in vitro they undergo about 50 cell population doublings at which time their growth rate begins to slow down and they finally die1,2. For this reason, several investigators have used the senescence of human fibroblasts in vitro as a model system for experimental ageing research3–6. One explanation for human fibroblast senescence is that some cell functions are lost before cells reach their maximum division limit. We have described the existence of a complex regulatory gene function controlling the inducibility of chromosome 21-directed anti-viral gene(s) (AVG) in human fibroblasts7. Our conclusions were derived from experiments on human fibroblasts monosomic, disomic or trisomic for chromosome 21. We therefore used all three cell types in this study to test the preservation of this complex regulatory gene function in fibroblasts allowed to age in vitro and in fibroblasts derived from human donors of different ages. We found (1) that no differences exist in AVG expression in human fibroblasts allowed to age in vitro and (2) that the AVG in human fibroblasts derived from older human donors (64 yr) is easier to induce than it is in younger donors (0–29 yr).

Heterochromatin and multiple inversions in a Drosophila chromosome.

Abstract: A chromosomal polymorphism is described from a Maui (Hawaii) population of D. disjuncta. The acquisition of an extra heterochromatic segment in a mitotic chromosome is specifically associated with ...

The site of 5S RNA genes in human chromosome 1.

Abstract: The major site of genes for human 5S RNA is in the long arm of chromosome 1. We find no evidence of sites in other chromosomes; if such exist, they are much smaller than the site in 1q.

Exclusion gene mapping utilizing patients with chromosome imbalance: the HL-A system as a prototype.

Abstract: 17 chromosomally unbalanced patients, their siblings and parents were tested for HL-A types and for up to 25 other polymorphic systems to determine whether there was gain or loss of an allele concurrent with the gain or loss of chromosome material. 5 patients had trisomy of part or all of a chromosome; 2 had trisomy of a segment and also deletion of chromosome material. All 7 were due to a familial translocation. The remaining patients had small deletions; 5 had ring chromosomes, 4 had rod deletions and 1 had missing chromosome material due to a heritable translocation. All cases were informative at the HL-A loci because of the high degree of polymorphism of the system whereas only some of the other systems were informative. None of the 17 patients showed unusual inheritance of HL-A or any other of the polymorphic systems examined. These results provide evidence excluding the HL-A and other loci from a number of possible locations in the human genome.

Karyotype and heterochromatin pattern of the field mouse,Apodemus argenteus Temminck

Abstract: The field mouse,Apodemus argenteus Temminck, has 46 chromosomes. The autosomes comprise 20 pairs of acrocentrics and 2 pairs of metacentrics. The X chromosome is represented by an outstandingly large submetacentric element, while the Y is an acrocentric corresponding in size to the 5th or 6th pair of autosomes. All of the autosomes and gonosomes can be unequivocally identified by their characteristic Q-band or G-band patterns. The constitutive heterochromatin, as revealed by C-banding, is localized at the centromeric regions of all autosomes, the short arm and the proximal 1/3 of the long arm of the X chromosome, and the entire Y chromosome. The C-band-positive segments which constitute 33.5% of the genome exhibit dark fluorescence after Q-banding, late DNA replication, faint or positive staining reaction to G-banding, fast reassociation of DNA revealed by AO staining, and allocyclic behavior of the sex-bivalent in male meiosis. An exception to the above is the distal segment of the Y which is positive to both C- and Q-banding. The giant X chromosome occupies 13.1% of the genome, leaving 5.6% of euchromatic segments, the latter value being equivalent to that of the original type X.

Isozyme analysis of somatic cell hybrids: assignment of the phosphoglucomutase 2 ( pgm 2 ) gene locus to chromosome 4 in man with data on the molecular structure and human chromosome assignments of six additional markers

Abstract: . The analysis of isozyme patterns of lysates of human-rodent somatic cell hybrids provides a convenient method for detecting the presence of human gene products in gene assignment studies and for obtaining data on the molecular structure of these gene products. The expression of human fumarate hydratase (FH) and guanylate kinase (GuK) in Chinese hamster-human somatic cell hybrids was found to be dependent upon the presence of chromosome 1 from man. FH appears to be a tetramer composed for four identical subunits while GuK may exist in monomeric form. Evidence for the monomeric structure of phosphoglucomutase 1 (PGM 1 ) and peptidase C (Pep C) isozymes and for the dimeric structure of 6-phosphogluconate dehydrogenase (PGD) isozymes in man was obtained; PGM 1 , Pep C , and PGD are also chromosome 1 markers in man. Data obtained have provided evidence that the isozymes related to the phosphoglucomutase 2 (PGM 2 ) and to the phosphoglucomutase 3 (PGM 3 ) gene loci in man are monomeric and that the PGM 2 gene locus can be assigned to human chromosome 4. Regional mapping indicates that it can be excluded from the distal portion of the long arm of this chromosome. Further evidence of the dimeric structure of the cytoplasmic form of glutamic oxaloacetic transaminase ( GOT 1 ) was obtained. The tentative assignments of the PGM 3 gene locus to chromosome 6, the gene loci for the cytoplasmic form of GOT and a high Km form of fibroblast hexokinase to chromosome 10 and the gene locus for the dimeric form of superoxide dismutase to chromosome 21 in man have been confirmed.

Somatic cell genetic analysis of the interferon system.

Abstract: Current advances in the use of somatic cell hybrid systems have enhanced the value of these systems for studying eukaryotic cell functions. We have reviewed the use of somatic cells to investigate the human interferon system. It has been shown that interspecific heterokaryons and hybrid cells can produce interferon(s) of both parental types and may be protected from viral challenge by interferon(s) from either parent. Using mouse-human hybrid cells we have assigned a human gene(s) responsible for regulating interferon to chromosome 21 and genes involved in the production of human interferon to chromosomes 2 and 5. Our data also suggest possible assignment of a locus involved in control of interferon production to chromosome 16. Suggested further uses of the somatic cell system for interferon studies include study of the subunit structure of interferons and the development of hybrid lines that produce human interferon at high levels (interferon/somatic cell hybrids/human gene assignment.

Three chromosome abnormalities (trisomy 21,XXY, and a de novo reciprocal translocation) in a child with 48,XXY,+21,t(6;10)(p22-24;p12)

Abstract: An infant with chromosomally normal parents was found to have double aneuploidy and a reciprocal translocation between chromosomes number 6 and 10. This cooccurrence may represent a very rare coincidence or may indicate that primary nondisjunction and chromosome rearrangements may be more than coincidentally related.

Clinical and cytogenetic aspects of the 21 deletion syndrome.

Abstract: The clinical, cytogenetic and dermatoglyphic findings in a patient with a ring chromosome 21 are presented. This anomaly acts as a deletion of chromosomal material and results in specific congenital defects. A comparison is made with 24 cases of deletions involving chromosome 21 described in the literature. Six of these have been studied by means of recently developed chromosome banding techniques. Cases presumably arise through somatic non-disjunction or chromosome breakage. When the chromosomes of both parents are normal the recurrence risk is negligible.

Is late replication of the inactive X chromosome irreversible in all cells of mammals

Abstract: The X chromosomes of the female bandicoot rat (Nesokia indica ) were 3H-thymidine labeled during two consecutive cell divisions to determine if all of the same segments of

Transmission of a t(13q22q) chromosome observed in three generations with segregation of the translocation D1-trisomy syndrome

Abstract: A case of an inherited type of D/G translocation D1-trisomy syndrome was described. A female proposita who had the clinical signs of D1-trisomy syndrome was found to have a chromosome complement of 46,XX,-G,+t(DqGq). Examination of Q- and G-stained karyotypes revealed that the chromosomes involved in the translocation were members of Nos. 13 and 22, or t(13q22q) with breaks at p12 of both chromosomes. C-stained figures also showed a large heterochromatin block in its centromeric region. The t(13q22q) chromosome was transmitted from the paternal grandmother of the proposita through at least three generations.

The location of repeated DNA sequences in the chromosomes of Chironomus tentans.

Abstract: Polytene chromosomes of Chironomus tentans were hybridized in situ with in vivo labelled nuclear and chromosomal RNA. Nuclear RNA formed hybrids preferentially in five distinct regions considered to contain clustered, repeated DNA sequences. These are the two nucleolar organizer regions, Balbiani ring 1 and 2, and the 5 S RNA genes in region 2A of chromosome II, which together comprised almost 70% of the total number of grains over the complement. The remaining grains were diffusely distributed over the chromosomes. There was a significant difference in the distribution of grains when RNA from different chromosomes was used for hybridization. Chromosome I RNA hybridized preferentially with chromosome I, and chromosome II+III RNA preferentially with chromosome II+III. Some regions within the chromosomes hybridized significantly more chromosomal RNA than other regions. A considerable cross-hybridization of RNA from one particular type of chromosome with the other chromosomes was also found. It is concluded that repeated DNA sequences which hybridize with heterogeneous chromosomal RNA in C. tentans are widely dispersed in the genome. Some of these sequences have a delimited localization, others are dispersed, and some sequences which are transcribed in one particular chromosome are present also in the other chromosomes.