Showing papers in "Cytogenetic and Genome Research in 1975"
TL;DR: A model based on DNA methylation is proposed to explain the initiation and maintenance of mammalian X inactivation and certain aspects of other permanent events in eukaryotic cell differentiation using sequence-specific DNA methylases that methylate unmethylated sites with great difficulty but easily methylate half-methylated sites.
Abstract: A model based on DNA methylation is proposed to explain the initiation and maintenance of mammalian X inactivation and certain aspects of other permanent events in eukaryotic cell differentiation. A key feature of the model is the proposal of sequence-specific DNA methylases that methylate unmethylated sites with great difficulty but easily methylate half-methylated sites. Although such enzymes have not yet been detected in eukaryotes, they are known in bacteria. An argument is presented, based on recent data on DNA-binding proteins, that DNA methylation should affect the binding of regulatory proteins. In support of the model, short reviews are included covering both mammalian X inactivation and bacterial restriction and modification enzymes.
1,114 citations
416 citations
TL;DR: Current attempts are directed to introduce a sufficient number of metacentrics in a defined background, thus providing the means for future systematic studies of the phenotypic expression of gross genomic imbalance.
Abstract: In pursuit of attempts at a systematic study of autosomal trisomy in the mouse, an experimental model is presented which permits the induction of specific trisomic conditions. It is based on (1) the occurrence of considerable rates of meiotic anaphase I malsegregation of double metacentric heterozygotes with monobrachial homology, (2) the expectation that trisomics may be found among the unbalanced conditions in the progeny of crosses of the double heterozygotes with "all acrocentric" mice, and (3) the observation that trisomy, in contrast to monosomy or combined monosomy plus trisomy, is the only unbalanced condition surviving beyond day 10. In this design, the specific nature of the trisomy is predetermined by the choice of the double metacentric heterozygote combination and recognized by such criteria as chromosome arm number and the presence of both metacentrics. All trisomic conditions of the mouse so far studied inevitably lead to early or late fetal death. Although the possibility of a systematic survey of all 19 possible autosomal trisomies in the mouse can be anticipated, this report is limited to a study of trisomies (Ts) 1, 8, 11, 12, and 17. Ts 8, 11, and 17 cause severe developmental inhibition at an early stage of development. Death occurs about day 11 or 12. Ts 1 displays a syndrome of moderate to marked developmental retardation and slight to more distinctly disproportionate hypoplasia. These embryos may survive until day 15. In contrast, a lesser extent of hypoplasia and retardation is observed in Ts 12, which, however, almost regularly shows exencephaly and microphtalmia. Obviously, variation of the severity of phenotypic manifestation of the trisomic conditions is due to genic heterogeneity of the animals used in the present study. Current attempts are directed to introduce a sufficient number of metacentrics in a defined background, thus providing the means for future systematic studies of the phenotypic expression of gross genomic imbalance.
207 citations
TL;DR: There were no large differences in the incidence of SCE between blood leukocyte chromosomes from male and female adults and newborn, and similar frequencies were found in cells from two patients with ataxia telangiectasia which, nevertheless, showed the typical increases in chromosomal aberrations.
Abstract: A new fluorescence plus Giemsa staining technique now makes the detection of sister-chromatid exchange (SCE) a relatively easy matter in cells containing 5-BrdU-substituted DNA. The technique has been
174 citations
TL;DR: It is evident from this study that the magnitude of chromosomal variation in human populations is far greater than heretofore believed and the combination of Q- and C-banding procedures will yield much more information than either technique used alone and is therefore the preferred approach to many population and gene localization studies.
Abstract: Chromosome preparations of 77 normal newborn babies from Grand Junction, Colorado, were stained first for G-band identification of each chromosome and subsequently stained for Q- and C-band localizati
163 citations
TL;DR: A system of nomenclature is proposed for identifying the origin and nature of these chromosomal rearrangements, and how additional functional centromeres are acquired in the reverse process of chromosomal fission or fragmentation.
Abstract: Translocations involving entire chromosomes or whole chromosome arms may not necessarily require deletion of a centromere. Conceivably, in the process of centromeric or telomeric fusion or of fusion of a centromere with a telomere, centromeric inactivation may occur, thus preserving both centromeres—one functional, the other latent—in the resultant translocation chromosome. If such latent centromeres exist and, in addition, are capable of being reactivated, it would explain how additional functional centromeres are acquired in the reverse process of chromosomal fission or fragmentation. A system of nomenclature is proposed for identifying the origin and nature of these chromosomal rearrangements.
148 citations
TL;DR: The term "variegated translocation mosaicism" is used to describe the repeated occurrence, within cultures of human skin fibroblasts, of a multiplicity of chromosomal rearrangements.
Abstract: The term “variegated translocation mosaicism” is used to describe the repeated occurrence, within cultures of human skin fibroblasts, of a multiplicity of chromosomal rearrangements. With respect to t
142 citations
TL;DR: The baseline data presented here reinforce the view that polymorphic chromosome characteristics are very useful markers for characterizing the karyotype of an infant born at the Albert Einstein College Hospital, Bronx, New York, and are consistent with the expectations of the Hardy-Weinberg law.
Abstract: Replicate chromosome preparations of umbilical-cord-blood leukocytes from 376 neonates born at the Albert Einstein College Hospital, Bronx, New York, were stained with C-, Q-, and G-banding methods to determine the frequencies and distributions of the variable chromosome bands. The C-band variants of primarily chromosomes 1, 9, and 16, as well as those of the remaining C, E, and F-group chromosomes, and the brightly fluorescing Q-band variants of chromosomes 3 and 4 and all of the acrocentrics, including the Y, were similarly analyzed. Polymorphism of these chromosome regions was so extensive that the idiogram of each of the 376 newborns of this study had a unique variant pattern, even when only the C- or only the Q-band patterns were compared. The distribution of polymorphic Q-bands in the population sampled was consistent with the expectations of the Hardy-Weinberg law, with the exception of chromosomes 3 and 22, where some deficiency of individuals with "homozygous" Q-band patterns was found. The baseline data presented here reinforce the view that polymorphic chromosome characteristics are very useful markers for characterizing the karyotype of an individual, for pedigree studies, for prenatal chromosome analyses, for population studies, for attempts at gene localizations, and for identifying specific cells or their chromosomes in somatic cell genetic studies.
131 citations
TL;DR: A technique is described for visualizing late-replicating regions by a Hoechst 33258-Geimsa-staining procedure combining the techniques of Latt and Perry and Wolff, which results in distinct bands obtained and many possible mistakes and interpretation difficulties with autoradiography are avoided.
Abstract: A technique is described for visualizing late-replicating regions by a Hoechst 33258-Giemsa-staining procedure combining the techniques of Latt (1973) and of Perry and Wolff (1974). The advantages are
107 citations
TL;DR: Chromosomal studies were performed on peripheral blood lymphocytes and cultured skin fibroblasts from five Israeli-Moroccan families with ataxia-telangiectasia and an apparent abnormal clone of cells was observed in varying proportions among cells of all the propositi.
Abstract: Chromosomal studies were performed on peripheral blood lymphocytes and cultured skin fibroblasts from five Israeli-Moroccan families with ataxia-telangiectasia. A total of 24 individuals, including seven propositi, was investigated. Among the probands, significantly elevated rates of chromosome damage were observed in both blood and skin. Skin fibroblasts of affected individuals showed several orders of magnitude more chromosome breakage than lymphocytes. Increased rates of chromosome damage were also observed in the fibroblasts of some phenotypically normal family members (obligate heterozygotes and sibs) when compared to normal controls. An apparent abnormal clone of cells, possessing a large acrocentric marker chromosome (14q+), was observed in varying proportions among cells of all the propositi (2-5% of lymphocytes; 1-9% of fibroblasts).
97 citations
TL;DR: A timetable for the initiation of DNA replication in human lymphocyte chromosomes has been established by a technique which allows detection of areas of chromosomes replicating at a given interval of the S-phase.
Abstract: A timetable for the initiation of DNA replication in human lymphocyte chromosomes has been established by a technique which allows detection of areas of chromosomes replicating at a given interval of the S-phase. The resolution of the method, using 33258 Hoechst-Giemsa staining, is more refined than that obtained with 3H-thymidine autoradiography. Early replicating regions coincide with R-bands. The timetable is rather coarse since replication may start asynchronously in the same region of homologous autosomes of the same metaphase and since even the sequence of bands appearing on individual chromosomes sometimes deviates from the rule.
TL;DR: Chromosome preparations were derived from short-term cultures of peripheral blood lymphocytes obtained from clinically normal dogs representing at least four breeds and most components of the canine karyotype can be distinguished readily.
Abstract: The canine metaphase karyotype consists of 78 chromosomes. All autosomes exhibit telocentric or acrocentric configurations gradually diminishing in size. These features make identification of homologo
TL;DR: An analysis of the pattern of association of acrocentric chromosome with nonacrocentric chromosomes in human lymphocyte metaphases was performed, finding a general preference for the centric regions, most pronounced at the proximal segments of the long arms of chromosomes 1, 9, and 16, which is interpreted to reflect heterochromatin attraction during interphase.
Abstract: An analysis of the pattern of association of acrocentric chromosomes with nonacrocentric chromosomes in human lymphocyte metaphases was performed. This pattern in nonrandom with respect to chromosome length and intrachromosomal distribution. There is a general preference for the centric regions, most pronounced at the proximal segments of the long arms of chromosomes 1, 9, and 16, which is interpreted to reflect heterochromatin attraction during interphase. Comparison of the association patterns of homologous chromosome 1's differing with regard to the size of their heterochromatic regions corroborates this interpretation. The possible significance of heterochromatin attraction for the formation of spontaneous and induced chromosome anomalies is discused.
TL;DR: A chromosome identification and karyotyping system for the Carnivora has been devised to facilitate comparison of data from future studies, and extensive interfamilial G-banding conservatism has been demonstrated.
Abstract: The Giemsa banding patterns of the chromosomes of 4 species of Procyonidae, 13 of Viverridae, and 6 of Felidae have been studied. The patterns have all been related to the basic felid karyotype. Each
TL;DR: A simple, reproducible microtechnique for obtaining metaphase chromosomes from peripheral blood of live mice and it has been successful with mice of several different genetic backgrounds and has been repeated in three other laboratories.
Abstract: We have developed a simple, reproducible microtechnique for obtaining metaphase chromosomes from peripheral blood of live mice. The method has been successful with mice of several different genetic backgrounds and has been repeated in three other laboratories.
TL;DR: A new technique of replica plating for CHO cells has been developed in which the pattern of colonies growing in a tissue culture plate is reproduced on a nylon cloth, which easily allows 10(4) colonies to be examined for mutant phenotypes.
Abstract: A new technique of replica plating for CHO cells has been developed in which the pattern of colonies growing in a tissue culture plate is reproduced on a nylon cloth. The efficiency of replica plating
TL;DR: Cytochemical measurements revealed that no cytological parameter of the two species conformed to the expected 2:1 ratio and every cytological factor of the tetraploid appeared to have been regulated toward the diploid level.
Abstract: Hyla versicolor (2n = 48) is a tetraploid counterpart to H. chrysoscelis (2n = 24). Cytochemical measurements revealed that no cytological parameter of the two species conformed to the expected 2:1 ratio. Every cytological factor of the tetraploid appeared to have been regulated toward the diploid level. H. versicolor-to-H. chrysoscelis mean ratios and their standard errors were: DNA, 1.90 ± 0.03; nuclear histone, 1.70 ± 0.18; nuclear RNA, 1.63 ± 0.19; total nuclear protein, 1.46 ± 0.05; nuclear sizes, 1.42 ± 0.08.
TL;DR: A model is presented which permits the analysis of C-banded diakinetic chromosomes as to whether crossing-over has occurred within the inversion segment or not and it was estimated that either one or two cross-overs had occurred in 52% of the cells within theInversion segment.
Abstract: Mitotic chromosome studies carried out on a newborn male infant with congenital abnormalities and on his family members showed that the father and paternal grandmother were heterozygotes for an unequa
TL;DR: The mitotic chromosomes of two species of gibbons are examined and compared, using various banding techniques, and it is difficult to propose a scheme for chromosomal evolution at this stage.
Abstract: The mitotic chromosomes of two species of gibbons (Hylobates lar and H. concolor) are examined and compared, using various banding techniques. These two species have very different karyotypes. At the most, seven pairs of chromosomes have a similar banding pattern. The other elements generally differ by complex structrual rearrangements. Thus, it is difficult to propose a scheme for chromosomal evolution at this stage. Comparison with the karyotypes of man and anthropoid apes also shows very important differences; very few chromosomes are common or only slightly modified. Some considerations about the hypothetical origin of particular chromosomal structures are given.
TL;DR: The karyotype of Akodon sp.
Abstract: Chromosomal polymorphism resulting from two pericentric inversions in Akodon arviculoides (2n = 14) has been described (Yonenaga, 1972a). In this paper the banding patterns are pres
TL;DR: The G- and C-banding patterns of Choeroniscus intermedius did not resemble those of Carollia, and the placement of these bat genera into different subfamilies is supported.
Abstract: A comparison of the chromosome banding patterns of the mitotic chromosomes of three species of bats of the genus Carollia and Choeroniscus intermedius revealed considerable banding pattern homology between the Carollia species but not between Carollia and Choeroniscus The G-band patterns of the chromosomes of the Carollia species were similar, but the C-band (heterochromatin) pattern of C castanea (Peru) lacked much of the heterochromatin common to the other two species C castanea also lacked the X-autosome translocation possessed by the other two species A system for denoting such sex-chromosome translocations is presented rather than presenting the chromosomes involved as multiple sex chromosomes The G- and C-banding patterns of Choeroniscus intermedius did not resemble those of Carollia, and the placement of these bat genera into different subfamilies is supported
TL;DR: Over 11,000 second meiotic metaphase spreads stained for the pericentromeric region have been studied quantitatively in male mice of 14 strains and nearly all the polyploid spreads were considered to arise by artifactual cell fusion at the time of second metaphase during the preparative technique.
Abstract: Over 11,000 second meiotic metaphase spreads stained for the pericentromeric region have been studied quantitatively in male mice of 14 strains The sex-chromosome constitution of a cell could be judg
TL;DR: The chromosomes of the Asian mice, Mus fulvidiventris (booduga?), are typical of the Mus in general, viz., 40 telocentric chromosomes, and the centromeric heterochromatin does not fluoresce brightly.
Abstract: The chromosomes of the Asian mice, Mus fulvidiventris (boodugal), are typical of the Mus in general, viz., 40 telocentric chromosomes. The centromeric heterochromatin does not fluoresce brightly. The G band pattern of the euchromatin is the same as that of M. musculus. The diploid number of M. dunni is also 40, but each autosome possesses a short, heterochromatic second arm. The X chromosome is a long submetacentric, whose entire short arm and the terminal segment of the long arm are heterochromatic. The Y is a long telocentric and is heterochromatic. The G band pattern of the long arms of M. dunni is again very similar to that of M. musculus. Thus, karyotypic changes in M. dunni involved only the addition of C bands. Mus dunni and M. booduga are sympatric in many localities in India, but they can be separated by karyological and subtle morphological differences.
TL;DR: A karyotype of the gibbon, Hylobates, has been prepared based on the chromosome banding patterns produced by quinacrine, trypsin-Giemsa, and centromeric heterochromatin stains, suggesting a relatively large evolutionary departure from the higher primates.
Abstract: A karyotype of the gibbon, Hylobates, has been prepared based on the chromosome banding patterns produced by quinacrine, trypsin-Giemsa, and centromeric heterochromatin stains The banding patterns of H lar and H moloch are virtually identical No brilliant quinacrine-fluorescent areas are present The banding pattern of most of the gibbon chromosomes show less resemblance to those of the human, chimpanzee, gorilla, or orangutan than the chromosomes of the higher primates do to each other, suggesting a relatively large evolutionary separation of the gibbon from the higher primates A pericentric inversion of chromosome 7 is present in one gibbon
TL;DR: OHNUKI's method for demonstrating coils in human metaphase chromosomes reveals a fine G-band pattern on prophase chromosomes of sufficient clarity to justify an attempt at mapping, and an intermediate stage in chromosome contraction.
Abstract: OHNUKI's method for demonstrating coils in human metaphase chromosomes also reveals a fine G-band pattern on prophase chromosomes of sufficient clarity to justify an attempt at mapping. Maps are provided for each chromosome to show the maximum number of prophase bands observed, and an intermediate stage in chromosome contraction, tracing the pathways of apparent band fusion as the cell progresses to metaphase, is presented. The prophase bands on many chromosomes tend to occur in distinct groups, the members of which ultimately merge to give the dark G-bands of metaphase chromosomes. Every G-band of the standard metaphase chromosomes. Every G-band of the standard metaphase pattern is compounded from two or more prophase bands. In at least contracted prophase chromosomes examined, some bands are seen which have no obvious metaphase counterpart. There are marked similarities between banded prophases and the chromoomere pattern seen at meiotic prophase. However, since chromosome contraction is a dynamic process, agreement between maps will be expected only for corresponding degrees of chromosome contraction.
TL;DR: Investigation of chromosome counts at metaphase II and karyotype analyses in early postimplantation embryos produced by backcrossing with chromosomally normal animals indicates that meiotic, gametic, and zygotic selection attributable to specific types of chromosomal imbalances is minimal, if any, by the late blastocyst stage.
Abstract: In heterozygous carriers of the mouse reciprocal translocation T(14;15)6Ca, the frequency of nondisjunction involving the minute marker chromosome was 4.4 % in the male and 22.2 % in the female. The fate of gametes with unbalanced genomes derived from normal as well as abnormal meiotic disjunction in T6 heterozygotes was investigated on the basis of chromosome counts at metaphase II and karyotype analyses in early postimplantation embryos produced by backcrossing with chromosomally normal animals. Results obtained indicate that meiotic, gametic, and zygotic selection attributable to specific types of chromosomal imbalances is minimal, if any, by the late blastocyst stage. All zygotes with unbalanced genomes, except those with 20 normal pairs plus the minute marker, however, die off in the latter half of pregnancy. Therefore, the increased incidence of translocation trisomics among progeny of female as compared with male heterozygotes reflects the higher incidence of nondisjunction in primary oocytes than in spermatocytes.