Showing papers on "Chromosome 22 published in 1981"
TL;DR: In situ hybridization to human metaphase chromosomes of the 3H-labeled cloned DNA resulted in highly significant labeling of band p36 of chromosome 1, such that 22% of all chromosome grains were located on this region.
Abstract: Recombinant lambda bacteriophage clone H3 containing a human DNA segment of 14.9 kb present in one or two copies per haploid genome was isolated. In situ hybridization in human metaphase chromosomes of the 3H-labeled cloned DNA resulted in highly significant labeling (53% of cells) of band p36 of chromosome 1, such that 22% of all chromosomal grains were located on this region. Hybridization was dependent upon the presence of dextran sulfate in the hybridization mixture and was not affected by repetitive DNA competitor. These results demonstrate localization of a single copy sequence on human metaphase chromosomes.
740 citations
TL;DR: Data from the literature are interpreted to suggest that DiGeorge's syndrome can be caused by deletion of a gene located in chromosome 22, probably in band 22q11.
Abstract: An association between DiGeorge's syndrome and an unbalanced chromosomal rearrangement leading to trisomy 20pter leads to 20q11 and monosomy 22pter leads to 22q11 was found in four individuals belongings to one family. These and other data from the literature are interpreted to suggest that DiGeorge's syndrome can be caused by deletion of a gene located in chromosome 22, probably in band 22q11.
335 citations
TL;DR: Fragments from section 3 of the salivary gland X chromosome of D. melanogaster were dissected with a micromanipulator and a sample of which were analysed and shown to contain Drosophila DNA which hybridises in situ to the region of section 2 of the X chromosome.
Abstract: Fragments from section 3 of the salivary gland X chromosome of D. melanogaster were dissected with a micromanipulator. The DNA was extracted, cut and ligated to a λ vector in a volume of a few nanoliters in an oil chamber monitored through a microscope. From about 10 pg of DNA we obtained 80 recombinant clones, a sample of which were analysed and shown to contain Drosophila DNA which hybridises in situ to the region of section 3 of the X chromosome. With this technique we can isolate clones from any desired region as small as 200 kb from the euchromatic arms of polytene chromosomes.
298 citations
TL;DR: The results demonstrate chromosomal localization of the human insulin gene to 11p15 and a significant percentage of hybridized cells exhibited silver grains on the distal end of the short arm (band p15) of chromosome 11.
Abstract: The human insulin gene was mapped by hybridization in situ of 3H-labeled recombinant plasmid pHIG900 to chromosome preparations in the presence of 10% dextran sulfate. pHIG900 contains a 900-base pair insert of human genomic DNA that includes the coding region for the C peptide and intervening sequence 2. A significant percentage of hybridized cells (34%) exhibited silver grains on the distal end of the short arm (band p15) of chromosome 11. Furthermore, silver grains on this region represented 26% of all chromosomal label. These results demonstrate chromosomal localization of the human insulin gene to 11p15.
277 citations
TL;DR: In this article, a series of rat liver cotransformed cell lines have been constructed containing from 5 to 100 copies of a variant human growth hormone gene, and they have been used hybridization in situ to demonstrate that most, if not all, COTransformed sequences reside in a chromosome of the host cell.
268 citations
TL;DR: The results indicate that human chromosome 22 carries the human λ immunoglobulin chain genes, and this cluster is assigned to human chromosome 14.
Abstract: Human immunoglobulin chains are expressed in somatic cell hybrids between mouse myeloma cells and human B cells1,2. By correlating the expression of human immunoglobulin chains and the presence of specific human chromosomes in the hybrid clones, we have assigned the human immunoglobulin heavy-chain gene cluster to human chromosome 14 (refs 1,2). We have now studied somatic cell hybrids between mouse myeloma cells and either human peripheral lymphocytes or different human λ chain-secreting lymphoblastoid cell lines. Somatic cell hybrid clones were pre-selected for their ability to produce human λ immunoglobulin chains, and studied for the expression of isozyme markers assigned to each of the different human chromosomes. Subclones of human λ chain-secreting hybrid clones were also studied. The results indicate that human chromosome 22 carries the human λ immunoglobulin chain genes.
195 citations
TL;DR: It is suggested that fragility of chromosomes generated as a result of early events in carcinogenesis may be one source of chromosome rearrangements, including those of chromosome #1, on which selection can operate and give rise to progressively more malignant clones.
142 citations
TL;DR: Viability of progeny from kar1 X KAR1 heterokaryons was improved when the parental nuclei were diploids to an extent consistent with the hypothesis, and diploid progeny which had become monosomic were recovered from these heterokARYons.
Abstract: Heterokaryons of Saccharomyces cerevisiae have been constructed utilizing the kar1-1 mutation, which prevents nuclear fusion during conjugation (J. Conde and G. Fink, Proc. Natl. Acad. Sci. U.S.A. 73:3651-3655, 1976). Each heterokaryon contained two haploid nuclei that were marked on several chromosomes. They segregated haploid progeny (cytoductants), most of which have the nuclear genotype of one or the other of the heterokaryon parents, but they occasionally segregated progeny having a recombinant genotype (exceptional cytoductants). Exceptional cytoductants receive the majority of their genome from one parent (the recipient) and a minority from the other (the donor). Transfer of two markers from the donor nucleus to the recipient is rarely coincident for markers located on different chromosomes but is nearly always coincident for those markers located on the same chromosome, suggesting that whole chromosomes are transferred from the donor nucleus to the recipient. In crosses of kar1-1 X KAR1 parents, either nucleus may act as a recipient or donor with equal probability. Recipient nuclei acquired 9 of the 10 chromosomes examined, with frequencies which were inversely correlated with the size of the chromosome. When a chromosome is acquired by the recipient nucleus, it either replaces its homolog or exists in a disomic condition. Haploid progeny emanating from kar1 X KAR1 crosses are frequently inviable. I tested whether this inviability might be the result of chromosome loss by donor nuclei. Viability of progeny from kar1 X KAR1 heterokaryons was improved when the parental nuclei were diploid to an extent consistent with the hypothesis, and diploid progeny which had become monosomic were recovered from these heterokaryons. The following sequence of events accounts for chromosome transfer in kar1 X KAR1 heterokaryons. After cell fusion, each nucleus in the heterokaryon has a probability of about 0.38 of losing one or more chromosomes. A nucleus sustaining such a loss can become a donor in a chromosome transfer event. If the other nucleus does not sustain a mortal chromosome loss, it can become a recipient in a transfer event. The chance of acquiring a chromosome lost by the donor is greater for smaller chromosomes than for larger ones and is about 0.05 for the average chromosome.
119 citations
TL;DR: Satellite DNA isolated from female Elapid snakes contains nucleotide sequences which are quantitatively derived from the W sex-determining chromosome, suggesting that this DNA is closely connected with the determination of sex.
Abstract: Satellite DNA isolated from female Elapid snakes contains nucleotide sequences which are quantitatively derived from the W sex-determining chromosome. Certain of these sequences are highly conserved in vertebrates, including mammals, where they are arranged in a sex-specific pattern in Southern blots. Sex reversed mice (Sxr) show a DNA arrangement of these sequences in conformity with their phenotypic sex, suggesting that this DNA is closely connected with the determination of sex. In situ hybridization of the snake sequences with mouse chromosomes reveals a concentration of related DNA at the proximal tip of the mouse Y chromosome. The possible nature and significance of these observations is discussed.
92 citations
TL;DR: Analysis of the human ONA sequences present in a human-mouse somatic cell hybrid line possessing a translocation involving human chromosomes 11 and X indicates that the human insulin gene is located on the short arm of chromosome 11 in the region p13→pter.
Abstract: The human insulin gene has been previously localized to chromosome 11. We have analyzed the human DNA sequences present in a human-mouse somatic cell hybrid line possessing a translocation involving human chromosomes 11 and X. These data indicate that the human insulin gene is located on the short arm of chromosome 11 in the region p13 leads to pter.
92 citations
TL;DR: Five somatic cell hybrids containing various combinations of mouse chromosomes, together with a constant set of hamster chromosomes, were tested for the presence of both genes using DNA restriction mapping techniques, suggesting a close functional relationship and a common evolutionary origin for α-fetoprotein and albumin.
Abstract: Several lines of evidence suggest a close functional relationship and a common evolutionary origin for alpha-fetoprotein and albumin. In the mouse, breeding studies have previously allowed the assignment of the albumin gene to chromosome 5. To test the possible linkage of alpha-fetoprotein and albumin, five somatic cell hybrids containing various combinations of mouse chromosomes, together with a constant set of hamster chromosomes, were tested for the presence of both genes using DNA restriction mapping techniques. Two of the five hybrids possessed both genes, and the other three lacked both. The only mouse chromosome present in the positive lines and absent from the negative ones was number 5, allowing the assignment of both genes to this chromosome.
TL;DR: Analysis of a single cell hybrid with a broken chromosome 2 indicates that the proopiocortin andACP1 genes are closely linked and in the distal region of the short arm of chromosome 2.
Abstract: The proopiocortin gene is located on chromosome 2 in humans. A 13-kb DNA fragment containing proopiocortin gene sequences was identified in human cells while proopiocortin-related genes sequences of 9.8 and 6.2 kb were present in mouse cells. In human-mouse cell hybrids which contained reduced numbers of human chromosomes and a complete set of mouse chromosomes, the 9.8- and 6.2-kb fragments were always present while the 13-kb fragment segregated with human chromosome 2 and the chromosome 2 enzyme markers acid phosphatase-1 (ACP1), malate dehydrogenase-1 (MDHI), and isocitrate dehydrogenase-1 (IDH1). Analysis of a single cell hybrid with a broken chromosome 2 indicates that the proopiocortin and ACP1 genes are closely linked and in the distal region of the short arm of chromosome 2.
TL;DR: In this paper, several recombinants were identified and purified from a cloned library of human DNA by virtue of their homology to DNA from a mouse-human hybrid cell line containing a single human chromosome, the X, and their lack of homologies to mouse DNA.
Abstract: Several recombinants were identified and purified from a cloned library of human DNA by virtue of their homology to DNA from a mouse-human hybrid cell line containing a single human chromosome, the X, and their lack of homology to mouse DNA. Three recombinants were characterized in detail, and all were homologous to reiterated DNA from the human X chromosome. These recombinants also were homologous to reiterated sequences on one or more human autosomes and, therefore, were not X chromosome specific. The recombinant DNA fragments homologous to human reiterated X DNA were the same fragments homologous to human reiterated autosomal DNA. Digestion of genomic DNAs with several restriction enzymes revealed that the pattern of fragments homologous to one recombinant, lambda Hb2, was the same on autosomes as on the X chromosome, suggesting that the molecular organization of these elements on the X is not distinct from their organization on autosomes.
TL;DR: This study demonstrates, for the first time, the fine structural details of chromosome uncoiling during a specific phase of the cell cycle and derives a new model of the Dinoflagellate chromonema.
Abstract: Members of theDinopbyceae are characterized by having permanently condensed chromosomes throughout the cell cycle. At interphase the chromosomes appear to have bands perpendicular to the long axis of the chromosome with a periodicity of 127 nm. Each band is composed of 2.5 nm fibers and 9.0 nm granules coiled into a helix around a central core of 9.0 nm fibers. Chromosome uncoiling has been correlated with the uptake of3[H]-thymidine. As chromosomes enter the uncoiling phase of the cell cycle they appear less dense and reveal a number of fibrous extensions. At later stages chromosomes completely uncoil into elongate fibers 127 nm in width. Chromosome unwinding corresponds to the peak in the uptake of3[H]-thymidine. Chromosomes observed on either side of the peak possess the typical interphase banding. This study demonstrates, for the first time, the fine structural details of chromosome uncoiling during a specific phase of the cell cycle. A new model of the Dinoflagellate chromonema has been derived from this study.
TL;DR: Results confirm the assignment of alpha-globin genes to HC16 and localize the genes to the short arm and assign the locus for phosphoglycollate to the long arm of HC16.
Abstract: The human α-globin and phosphoglycollate phosphatase (EC 3.1.3.18) genes have been regionally localized to the short arm of human chromosome 16 (HC16). This was accomplished by fusing mouse fibroblasts (A9) to human fibroblasts that contain a reciprocal translocation between the long arms of chromosomes 16 and 11. The murine A9 cells are deficient in adenine phosphoribosyltransferase (APRT), an enzyme present on the long arm of HC16 (HC16q). Hybrid cells were grown in selection culture medium that required the cells to retain human APRT. Therefore, the hybrids exhibited stable retention of the entire HC16 or the rearranged chromosome containing HC16q. We isolated five independent primary and secondary hybrid cell lines which retained either HC16 or HC16q at a high frequency. The presence of human α-globin genes in the various clones was established directly by DNA extraction and hybridization to a cDNA probe for human α-globin genes. Autoradiographs showed that hybrid cells containing the long arm, but not the short arm, of HC16 showed only the background mouse bands. Hybrid cells that retained the entire HC16 demonstrated the band(s) containing the human α-globin genes. Hybrid cells that contained HC16 with its α-globin genes were then placed in culture medium that contained diaminopurine, which is lethal for cells containing APRT. These counter-selected hybrid cells had lost HC16 and also lost the human α-globin genes as determined by blot hybridization. The presence of α-globin gene sequences in the hybrid clones was concordant with HC16 only and not with any other human chromosome. These results confirm the assignment of α-globin genes to HC16 and localize the genes to the short arm. We also assign the locus for phosphoglycollate to the short arm of HC16.
TL;DR: On the basis of a comparison of the clinical features in full trisomy 13, partial 13 trisomies, 13 rings, 13 deletions, and CES the small marker present in this syndrome is considered to be a chromosome 13 with an interstitial deletion.
Abstract: The cat eye syndrome (CES), usually ascribed to the presence of a deleted supernumerary 22 chromosome, is characterised by a typical clinical picture including anal atresia, ocular coloboma, preauricular tags or sinuses, congenital heart defects, urinary tracts anomalies, and mental and physical retardation An analysis of published reports revealed that of the 57 reported cases, only 21 showed the complete form, and 11 had a normal karyotype Several observations question the existence of a trisomy 22:(1) the absence of any report in living subjects of trisomy 22 arising from an inherited Robertsonian translocation; (2) the recurrent abortions in carriers of Robertsonian translocations involving chromosome 22; and (3) the existence of a syndrome, showing the same clinical features as trisomy 22, which is irrefutably dependent on a trisomy of the distal region of the 11 long arm On the basis of a comparison of the clinical features in full trisomy 13, partial 13 trisomies, 13 rings, 13 deletions, and CES the small marker present in this syndrome is considered to be a chromosome 13 with an interstitial deletion An attempt to map this chromosome has been made
TL;DR: G-banding patterns in somatic cells allowed identification of the chromosome pairs involved in centric fusion and the presence of constitutive heterochromatin near the centromere the X chromosome and those of the autosomes in Oryzomys subflavus.
Abstract: Eighty-four specimens of Oryzomys subflavus, collected in the State of Pernambuco, Brazil, were studied. A Robertsonian chromosome polymorphism, characterized by a varying diploid number of 50, 49, 48, and 46, was found. All the specimens showed a chromosome arm number of 56. G-banding patterns in somatic cells allowed identification of the chromosome pairs (2, 3, 5, and 7) involved in centric fusion. C-banding revealed the presence of constitutive heterochromatin near the centromere the X chromosome and those of the autosomes. The Y chromosome presented a large heterochromatic block in the distal portion of its long arm.
TL;DR: Evidence is presented from C-banding studies that the W chromosome of eleven species of snakes is not homogeneous in nature but is differentiated linearly into alternating lighter and darker C positive regions, and the significance of heterochromatinization as a means of generating differentiated sex chromosomes is discussed.
Abstract: Evidence is presented from C-banding studies that the W chromosome of eleven species of snakes is not homogeneous in nature but is differentiated linearly into alternating lighter and darker C positive regions. The same is true of the W chromosome of at least some birds. There is evidence from the literature indicating a similar differentiation of the Y chromosome of some mammals and here the intermediate C positive regions are deficient in highly repetitive DNA. The significance of heterochromatinization as a means of generating differentiated sex chromosomes is discussed in the light of these findings.
TL;DR: The DNA in the major portion of the enlarged short arm was highly methylated, as shown by the binding of antibodies to 5-methylcytidine after UV-denaturation of chromosomal DNA.
Abstract: The banding characteristics of an extreme variant familial chromosome 22 short-arm enlargement are described. Ag-AS staining for nucleolar-organizer regions, identified two areas of rDNA actively coding for 18S and 28S rRNA, the one being a broad distal Ag-band and the other a narrower centromeric Ag-band. The DNA in the major portion of the enlarged short arm was highly methylated, as shown by the binding of antibodies to 5-methylcytidine after UV-denaturation of chromosomal DNA. Mean Ag-band size on the aberrant 22p+ correlated with the mean number of 22p+ associations. Association of 22p+ was no greater than that of other acrocentrics, in spite of a presumed excess number of rDNA gene copies. This case represents only the second such normal variant defined by these techniques.
TL;DR: Measurements of red-cell levels of esterase D (ESD) showed a 50% increase in ESD activity, which suggests noninactivation of the ESD locus on the der(X) chromosome, a finding consistent with the late-replication data.
Abstract: Chromosome replication pattern was reevaluated in an unbalanced X/13 translocation carrier, 46, X, der (X), t(X;13)(q27;q12), using the BudR-acridine orange technique. The translocated chromosome, Xpter→q27::13q12→13qter, was late replicating in all analyzed cells. The autosomal segment showed a replication pattern comparable to the two normal, and presumably genetically active, chromosome 13’s, with the exception of band 13q22, which was consistently late replicating. Measurements of red-cell levels of esterase D (ESD) (a marker assigned to 13ql4) showed a 50% increase in ESD activity, compared to that in normal controls and parents of the patient. This suggests noninactivation of the ESD locus on the der(X) chromosome, a finding consistent with the late-replication data.
TL;DR: The cytochemical and autoradiographic results reveal that the dot chromosome is transcriptionally active and is not late-replicating, as is expected of α-heterochromatin, and this is the first report of an under-replicated autosomal locus which is not located in heterochromatic blocks.
Abstract: Using in situ nucleic acid hybridizations, the genes that code for 28, 18 and 5S rRNA have been localized in the polytene chromosomes of Drosophila tumiditarsus. The 5S genes are found at a single site near the centromere of the second chromosome, whereas the 28 and 18S genes are found at the nucleolar organizer region of the dot chromosome. The dot chromosome has been previously described as α-heterochromatic. However, our cytochemical and autoradiographic results do not support such a conclusion. The autoradiographic results reveal that the dot chromosome is transcriptionally active and is not late-replicating, as is expected of α-heterochromatin. Further, the dot chromosomes possess none of the usual staining characteristics of heterochromatin except for its lack of polytene bands. Using rRNA-DNA filter hybridizations, we find that the rDNA of D. tumiditarsus salivary glands is under-replicated. This is the first species of Drosophila where the rDNA in not found on the sex chromosomes, and is the first report of an under-replicated autosomal locus which is not located in heterochromatic blocks.
TL;DR: Evidence for another syntenic relationship that has been conserved is found by regional mapping of human DIA1 and ARSA using somatic cell hybrids segregating a human chromosome translocation t(15;22)(q14;q13.31).
Abstract: We have utilized a panel of Chinese hamster × mouse somatic cell hybrids segregating mouse chromosomes to assign a gene for arylsulfatase A (ARSA) to mouse chromosome 15. Considering our previous assi
TL;DR: Though the existence of Rex is known only from its effects on behavior of a particular compound chromosome, it presents intriguing possibilities for understanding regulation of chromosome behavior and organization of the ribosomal cistrons.
Abstract: Multiple copies of the 18s and 28s ribosomal RNA cistrons are present in both the X and Y chromosomes of Drosophila melanogaster. Data are presented here that identify a locus, Rex, that causes exchange-like events between duplicated ribosomal complexes at the ends of an attached-XY chromosome. Rex: (1) is close to or in the basal heterochromatin of the X chromosome; (2) is semidominant and (its effect) is temperature sensitive; (3) acts maternally; and (4) affects behavior of paternally derived attached-XY chromosomes shortly after fertilization. Though, at this point, the existence of Rex is known only from its effects on behavior of a particular compound chromosome, it presents intriguing possibilities for understanding regulation of chromosome behavior and organization of the ribosomal cistrons.
TL;DR: The karyotype-phenotype correlations in the men with this aberrant Y chromosome, especially the fertility dysfunctions (oligoasthenoteratozoospermia, cryptozoospermia), are discussed.
Abstract: Comparative cytogenetic analyses were performed with ten different banding methods on a previously undescribed, inherited structural aberration of a Y chromosome, and the results compared with those of normal Y chromosomes occurring in the same family The value of the individual staining techniques in investigations of Y chromosomal aberrations is emphasized The aberrant Y chromosome analyzed can be formally derived from an isodicentric Y chromosome for the short arm with a very terminal long-arm breakpoint, in which the centromere, an entire short arm, and the proximal region on one long arm was lost This interpretation was confirmed by determining the amount of the two Y-specific DNA sequences (21 and 34 kb in length) by means of HaeIII restriction endonuclease analysis The karyotype-phenotype correlations in the men with this aberrant Y chromosome, especially the fertility dysfunctions (oligoasthenoteratozoospermia, cryptozoospermia), are discussed The possibility of the existence of fertility factors involved in the control of spermatogenesis within the quinacrine-bright heterochromatic region of the Y long arm is presented
TL;DR: Two forms of intraspecific heterochromatin variations, involving three types of chromosomes, are described: 1) differences in the fluorescence pattern with regard to the Y chromosome and the centromeric heterchromatin of the pair II; 2) Differences in the size of theheterochromatic segment of the X chromosome.
Abstract: Neuroblast chromosomes of 16 Drosophila melanogaster laboratory stocks (15 wild type and 1 carrying the mutant vermilion) were carefully analyzed for Q-banding patterns and morphological characteristics, in all the mitotic phases. Two forms of intraspecific heterochromatin variations, involving three types of chromosomes, are described: 1) differences in the fluorescence pattern with regard to the Y chromosome and the centromeric heterochromatin of the pair II; 2) differences in the size of the heterochromatic segment of the X chromosome. An unambigous evidence of such variants was obtained by comparing homologous chromosomes in the F1 hybrids, as well as in the F2 offspring, where differences in appearance of the heteromorphic chromosomes was readily identified as to the parental origin. The possible evolutionary significance and the usefulness of such cytologically detectable genetic differences between various strains, are considered.
Journal Article•
TL;DR: Reversion to the tk- phenotype seems to involve discrete deletions of transforming DNA without apparent chromosome loss in this restricted set of mutants, it thus seems crucial to maintain the diploid chromosomal complement.
Abstract: We have constructed a series of tk+ cell lines by DNA-mediated gene transfer to correlate chromosomal behavior and DNA sequence alterations associated with reversion to the tk- phenotype. Tk- revertants were selected from each of four well-characterized transformed cell lines containing the viral tk gene and multiple human growth hormone genes (HGH). Tk- colonies were analyzed for the presence of tk and HGH sequences by blot hybridization to restriction endonuclease cleaved DNA. Revertants were further characterized by detailed karyotype analysis and hybridization in situ. Blot hybridization of forty tk- revertants indicates that over half of the revertants delete all of the transforming DNA from the recipient chromosome. In fifteen additional revertants, significant deletion has occurred, although transforming DNA is retained. The analysis of chromosomes by Giemsa banding together with hybridization in situ reveals that the deletion of transforming DNA is never associated with loss of an entire chromosome. Reversion to the tk- phenotype, therefore, seems to involve discrete deletions of transforming DNA without apparent chromosome loss. In this restricted set of mutants, it thus seems crucial to maintain the diploid chromosomal complement.
Journal Article•
TL;DR: Four cases of attachment of chromosome material at the ends of normal chromosomes in Drosophila are presented to serve as a parallel to cases of apparent terminal breakage and reunion in certain rearrangements in man.
Abstract: Descriptions are presented of four cases of attachment of chromosome material at the ends of normal chromosomes in Drosophila. Since no material appears to be missing from the polytene chromosomes and there are no ill effects to the organism in morphology, viability, or fertility when the chromosome is made homozygous, it is argued that the attachment occurred without the loss of any essential genetic material and that, in all probability, the break at the end of the chromosome occurred within the telomere of the chromosome. These cases may serve as a parallel to cases of apparent terminal breakage and reunion in certain rearrangements in man.
Journal Article•
TL;DR: The chromosomes of two patients with ring 13 (r13) were studied using high-resolution RBG banding of prometaphase cells to discuss the evolution of these cell lines as a result of sister chromatid exchange, nondisjunction, ring breakage, and premature chromosome condensation.
Abstract: The chromosomes of two patients with ring 13 (r13) were studied using high-resolution RBG banding of prometaphase cells. The rings of the two patients differ slightly in breakpoints. Cell with multiple single, double-sized rings, quadruple-sized rings, rod- and ring-shaped fragments, and fragments showing varied states of condensation were seen, as were cells monosomic for chromosome 13. The evolution of these cell lines as a result of sister chromatid exchange, nondisjunction, ring breakage, and premature chromosome condensation is discussed. Clinical features of these patients reflect the heterogeneity of phenotype for r13 patients. Each case includes a feature of trisomy 13. The significance of mosaicism of cell lines in patients bearing ring chromosomes is considered with respect to variation in clinical findings.
TL;DR: The atypical chromosome had a quite similar replication pattern to the late replicating X chromosome of the normal woman, suggesting that its sequence of DNA synthesis was not altered.
Abstract: The morphologic and staining characteristics of the sex chromatin bodies and the DNA replication patterns were studied in a patient with a 45,X/46,X,idic(X)(p22.3::p22.3) karyotype and in a normal woman. The analysis showed a relatively high frequency of bipartite Barr bodies as well as some variation of the distance, staining intensity, and size relationship between their halves. Regarding the DNA replication studies, in 71% of the cells the abnormal X chromosome showed a synchronous pattern, and in the remaining 29%, in which a slight asynchrony was present, an almost equal proportion of early and late functional and nonfunctional centric halves was observed. Furthermore, the atypical chromosome had a quite similar replication pattern to the late replicating X chromosome of the normal woman, suggesting that its sequence of DNA synthesis was not altered.
TL;DR: Three categories of chromosome manipulation are discussed, with examples from hexaploid wheat: manipulations associated with a male-sterility mutation on chromosome 4A and the distinctive genetic activities of this chromosome, and exchanges between homoeologous groups 2 and 4.
Abstract: Three categories of chromosome manipulation are discussed, with examples from hexaploid wheat. First, uncontrolled events, such as intergeneric translocations induced by mutagenic agents, have been frequently isolated but have been infrequently incorporated into widely grown varieties. A method proposed by K. W. Shepherd is designed to select an accommodating genetic background for these interchanges and thereby overcome this deficiency. This relies on selection for yield among many selections that are homozygous for a translocation but segregating for many other genetic components. The second category involves manipulations associated with the distinctive genetic activity of chromosome 5B. ph mutants are expected to play an important role in the transfer of genetic material from other genera to wheat. A method described by E. R. Sears is designed to isolate a small intercalated alien segment. This relies on crossing-over in an alien segment that is common to two distinct types of homoeologous-exchange chromosomes. The third category involves manipulations associated with a male-sterility mutation on chromosome 4A and the distinctive genetic activities of this chromosome. A method, described by the author, is designed to produce hybrid wheat with an induced male-sterility mutation on this chromosome. Fertility restoration is being attempted with four chromosomes, a restriction on which is that they must not pair with the other chromosomes of the wheat complement. These are a modified 4A -2R translocation chromosome, part of the cereal rye genome, chromosome 4 of barley, and chromosome 4 of diploid wheat. It appears that chromosome 4A originated elsewhere than from diploid wheat; thus the A genome of common wheat arose from at least two species. As detected by M. A. Hossain and the author, part of the genetic material for male fertility on 4A has a counterpart on rye chromosome 2R. An exchange between the chromosomes of homoeologous groups 2 and 4 appears to have occurred, perhaps at the diploid level.