DNA Content Of Individual Chromosomes Research Articles

Effect of mosaic pattern of trisomy in autosome or sex chromosome on recurrent abortions

The DNA content of some Zea mays chromosomes has been measured by flow karyotyping because similar chromosomes could not been discriminated. This technique requires suspensions with a high amount of intact chromosomes and protocols that provide enough resolution to quantify the DNA content of individual chromosomes. In order to measure the DNA content of A and B chromosomes of Z. mays ‘Black Mexican Sweet Corn’, we associated cytogenetic, flow and image cytometry tools. The cytogenetic methodology provided slides with A and B chromosomes adequate for karyogram assembly. The flow cytometry histograms exhibited distinct G0/G1 and G2 peaks for ‘Black Mexican Sweet Corn’ with (sample) and without (standard) B chromosomes. As a result, the nuclear DNA content of five plants showing B chromosomes was quantified. The nuclear genome size value was proportionally distributed according to the integrated optical density value, which was measured for individual chromosomes by image cytometry. Then, the DNA content of each A and B chromosome was calculated in picograms and base pairs. Based on qualitative (cytogenetic) and quantitative (flow and image cytometry) analyses, it was possible to discriminate and characterize the A and B chromosomes of ‘Black Mexican Sweet Corn’.

DNA content of individual chromosomes of Chinese hamster normal karyotype and its permanent cell lines V-79 RJK and Verb-5

The genome size of the Chinese hamster Cricetulus griseus, absolute and relative DNA content of individual chromosomes in normal Chinese hamster karyotype and Chinese hamster cell lines V-79 RJK and Vebr-5 during long-term cultivation were determined with flow cytometry and microfluorimetry. It has been shown that the genome size of Chinese hamster males and females is 6.660 and 6.746 pg, respectively. DNA content in chromosomes of the cultivated cells drastically differed from that the normal Chinese hamster karyotype. It changed during the long-term cultivation of both cell lines. In certain chromosomes, the changes reached 20–25% (as a rule, increased). The level of DNA amplification in the p-arm of chromosome Z6 in cells Vebr-5 registered at the beginning of the experiment in the course of further cellular cultivation (over 20 years) remained stable. The data obtained suggest that the cell malignant transformation and cellular adaptation to the conditions in vitro resulted in the dramatic genome restructuring affected all chromosomes.

DNA image-fluorimetry of individual human chromosomes

Mucrofluorimetric method for the determination of DNA content in individual human chromosomes has been developed. The method is based on a preliminary identification of chromosomes with Hoechst 33258, followed by staining of the chromosomes with Feulgen reaction using Schiffs reagent type ethidium bromide-SO2, then measuring the fluorescence intensity of the chromosomes using an image analyzer. The method allows to determine the DNA content of individual chromosomes with accuracy up to 4.5 fg. DNA content of individual human chromosomes, their p-and q-arms as well as homologous chromosomes were measured using the developed method. It has been shown that the DNA content in the chromosomes of normal human karyotype is unstable. Fluctuations in the DNA content in some chromosomes can vary 35-40 fg.

An integrated cytogenetic, flow and image cytometry procedure used to measure the DNA content of Zea mays A and B chromosomes

The DNA content of some Zea mays chromosomes has been measured by flow karyotyping because similar chromosomes could not been discriminated. This technique requires suspensions with a high amount of intact chromosomes and protocols that provide enough resolution to quantify the DNA content of individual chromosomes. In order to measure the DNA content of A and B chromosomes of Z. mays ‘Black Mexican Sweet Corn’, we associated cytogenetic, flow and image cytometry tools. The cytogenetic methodology provided slides with A and B chromosomes adequate for karyogram assembly. The flow cytometry histograms exhibited distinct G 0/G 1 and G 2 peaks for ‘Black Mexican Sweet Corn’ with (sample) and without (standard) B chromosomes. As a result, the nuclear DNA content of five plants showing B chromosomes was quantified. The nuclear genome size value was proportionally distributed according to the integrated optical density value, which was measured for individual chromosomes by image cytometry. Then, the DNA content of each A and B chromosome was calculated in picograms and base pairs. Based on qualitative (cytogenetic) and quantitative (flow and image cytometry) analyses, it was possible to discriminate and characterize the A and B chromosomes of ‘Black Mexican Sweet Corn’.

Chromosomal DNA content of sweet pepper determined by association of cytogenetic and cytometric tools

The nuclear DNA content of sweet pepper (Capsicum annuum L. var. annuum, 2n = 24) has been measured by flow and image cytometries but the DNA content of each chromosome of this species has not yet been regarded. DNA content of individual chromosomes has been quantified by the flow karyotyping technique, which requires a great quantity of intact metaphasic chromosomes and methods that allow the characterization of individual chromosomes; however, the obtainment of adequate number of metaphases can be difficult in some species like C. annuum. In order to estimate the DNA content of each C. annuum var. annuum cv. "New Mexican" chromosome, flow and image cytometries were associated with the cytogenetic methodology. First, the DNA amount (2C = 6.90 pg) was established by flow cytometry. Integrated optical density (IOD) values were calculated by image cytometry for each Feulgen stained metaphasic chromosome. Then, by distributing the correspondent metaphasic value (4C = 13.80 pg) proportionally to average IOD values, the following chromosomal DNA contents were obtained in pg: 0.74 (chromosome 1), 0.67 (2), 0.61 (3, 4), 0.60 (5), 0.59 (6, 7), 0.58 (8), 0.57 (9), 0.56 (10) and 0.39 (11, 12). This study reports an alternative and reproducible technique that makes quantifying the chromosomal DNA content possible.

The role of chromosomes in the characterisation of human neoplasms

Observations reported in the literature, since 1959, have been assessed and analysed for chromosome number per cell (ploidy levels) and karyotype (number of chromosomes per classification group, structure and DNA content of individual chromosomes). Measurements of chromosome size are presented, to show how the genetical balance of chromosomal types within a karyotype can be determined in pseudodiploid and aneuploid cells. These findings are discussed in relation to the role of chromosome anomalies in cell metabolism, malignant transformation and Boveri's theory that chromosome anomalies cause cancer. Objections to Boveri's Theory arise from the occurrence of (a) certain aneuploid pathological conditions and cell lines that are non-malignant, and (b) diploid primary and secondary malignant neoplasms with apparently normal karyotype. However, studies on families have indicated that syndromes due to chromosome anomalies may predispose cells for malignant transformation because of their metabolic instability; and the possibility remains that apparently diploid neoplasms may be pseudodiploid (and await further techniques for their detection). Evidently, chromosome anomalies have a metabolic effect in neoplasms and are of considerable importance in aiding the progression of neoplasms towards greater malignancy. The selective advantage of cell variants results in the evolution of characteristic ploidy levels of tumours at different sites. Chromosome studies may aid the diagnosis of malignancy in some neoplasms, where striking changes in the chromosome constitution is directly associated with their capacity for invasion.

DNA content of wheat monosomics at interphase estimated by flow cytometry

Two complete, independently maintained sets of 21 monosomic wheat lines derived from cv. ‘Chinese Spring’ were analyzed for their DNA content at the G1 stage with flow cytometry. The DNA content of individual chromosomes was estimated by subtracting the value of a monosomic line from that of euploid wheat. Our data show that the estimated 2C DNA of individual wheat chromosomes in 21 monosomics at the G1 stage ranges from about 0.58 pg in chromosome 1D to approximately 1.12 pg in chromosome 3A. The A genome (2C=6.15 pg) seems to contain more DNA than the B (2C=6.09 pg) and D (2C=5.05 pg) genomes. Analysis of variance showed significant differences (α=0.01) in DNA content both among homoeologous groups and among genomes. Our estimates of interphase DNA content of wheat chromosomes from monosomic lines were poorly correlated to the chromosome sizes at metaphase (r=0.622, P≤0.01). This poor correlation might be due to differential coiling among chromosomes during cell division, possible bias of fluorochrome binding to heterochromatin, or heterogeneity among monosomic lines. Finally, flow cytometry may aid but cannot replace cytological checks in aneuploid maintenance.

Classification of Y chromosome polymorphisms by DNA content and C-banding.

A system has been developed using a microscope photometer to measure the DNA content of individual chromosomes. After correcting for the systematic and statistical errors the measured values are highly reproducible. Data are presented of measurements of human Y chromosomes from a cytogenetically normal population. When compared with the C-banding pattern from the same specimens the DNA content is found to change in discrete steps of 1.36 x 10(-14)g or 13.26 x 10(6) bp for each of the Y chromosome polymorphic types.

Flow cytometric DNA and cytogenetic studies in human tumors: a comparison and discussion of the differences in modal values obtained by the two methods.

The numerical chromosome values in 53 human tumors were determined and compared with the modal DNA values as measured by flow cytometry. In tumors with chromosome counts in the diploid and tetraploid range, the modal DNA values were found to correspond to the modal values based on the chromosome counts. In tumors with chromosome counts in the triploid range, however, the modal DNA values were about 15% higher than expected. In order to explain this difference, the ratio between large and small chromosomes in the karyotyped metaphases was assessed. In addition, the DNA content of individual chromosomes, including markers and minutes, was calculated as a reflection of the DNA content of the whole cell. The ratio of large to small chromosomes did not deviate from the normal ratio found in cells with diploid, triploid, and tetraploid chromosome counts. Neither difficulties in karyotyping nor short-comings in the flow cytometric methodology could be used to explain the discrepancy between the expected and empirical modal DNA values. Some of the chromosomes in triploid tumors may, therefore, contain an increased amount of DNA.

Variation in DNA content of 21 individual chromosomes among six subspecies in common wheat.

In order to consider at chromosomal level the phylogeny of wheat, DNA content of 21 individual chromosomes was measured cytophotometrically at M1 or A1 of meiosis in monosomic plants and compared among seven strains belonging to six subspecies of common wheat, Triticum aestivum.1) Nuclear DNA content at pollen tetrad did not differ at all among seven strains.2) DNA content of individual chromosomes varied from chromosome to chromosome in any strain.3) Significant difference was found among three genomes, A, B and D, the ratio being 1.14:1.21:1.00. This ratio apparently differed from those of two earlier reports based on nuclear DNA content of putative diploid ancestors (T. monococcum: Aegilops speltoides: Ae. squarrosa). The authors suggested diploid species of section Sitopsis, with a little higher DNA content than Ae. speltoides as B genome donor to polyploid wheat.4) There was not significant difference among seven homoeologous groups, but homologous chromosomes.5) Total DNA content of seven strains calculated from DNA content of individual chromosomes was very similar to one another, being clearly compatible with the results of nuclear DNA content at pollen tetrad.

The DNA content of the individual chromosomes of rye

The relative DNA content of individual chromosomes of Secale cereale L. was determined in 25 cells by microdensitometry of Feulgen stained preparations. The correlation value between relative DNA content and relative chromosome length was r=0.61 for all 328 chromosomes measured. However, the correlation coefficients calculated for individual cells as well as for mean values always approached 1. Taking into account the structure of rye chromosomes, this indicates that microdensitometric results may not be accurate when large quantities of heterochromatic DNA sequences are present in analyzed material.

Relative DNA content of individual chromosomes, karyotype and ploidy in crown gall tumor cells of Crepis capillaris.

Levels of ploidy, karyotype, mitosis and relative DNA content of chromosomes in crown gall tumor cells in stem and leaf of Crepis capillaris were studied. Except for about 7% tetraploid mitoses, dividing cells were found to be mainly diploid in both stem and leaf tumors. The karyotype and mitosis in tumor cells were not detectably different from normal cells. The relative DNA content of homologous pairs of chromosomes in the genome of tumor cells was similar to that of root tip cells. These observations indicate that no dramatic change in DNA content or DNA distribution occurred when tissue was transformed to crown gall tumor.

The role of chromosomes in the characterisation of human neoplasms

Observations reported in the literature, since 1959, have been assessed and analysed for chromosome number per cell (ploidy levels) and karyotype (number of chromosomes per classification group, structure and DNA content of individual chromosomes). Measurements of chromosome size are presented, to show how the genetical balance of chromosomal types within a karyotype can be determined in pseudodiploid and aneuploid cells. These findings are discussed in relation to the role of chromosome anomalies in cell metabolism, malignant transformation and Boveri's theory that chromosome anomalies cause cancer. Objections to Boveri's Theory arise from the occurrence of (a) certain aneuploid pathological conditions and cell lines that are non-malignant, and (b) diploid primary and secondary malignant neoplasms with apparently normal karyotype. However, studies on families have indicated that syndromes due to chromosome anomalies may predispose cells for malignant transformation because of their metabolic instability; and the possibility remains that apparently diploid neoplasms may be pseudodiploid (and await further techniques for their detection). Evidently, chromosome anomalies have a metabolic effect in neoplasms and are of considerable importance in aiding the progression of neoplasms towards greater malignancy. The selective advantage of cell variants results in the evolution of characteristic ploidy levels of tumours at different sites. Chromosome studies may aid the diagnosis of malignancy in some neoplasms, where striking changes in the chromosome constitution is directly associated with their capacity for invasion.