Late Prophase Chromosomes Research Articles

Identification of the chromosomes of rye by distribution patterns of DNA.

Ultramicrospectrophotometric measurements were made on unstained and Feulgen-stained rye chromosomes at 265 mμ and 546 mμ, respectively. The total extinction values of the individual chromosomes corresponded to their relative lengths. Similarly, the long/short arm extinction values agreed well with the index ratios, and were thus useful for the classification of the chromosomes into groups. The distribution of the nucleic acids along the chromosomes was determined by scanning individual chromosomes transversally and in a few instances longitudinally. More details were found in the pattern curves obtained from measurements made on unstained than stained chromosomes. Also the greater the length of the chromosome, the greater was the detail that could be seen. The distribution pattern of DNA was in accordance with the heteropycnotic differentiation along late prophase chromosomes. A specific pattern of nucleic acid distribution along each of the seven chromosome types was useful for chromosome identification. In the pattern curves, sites indicating a markedly low nucleic acid content coincided with the positions of primary and secondary constrictions. Sites with slightly lower nucleic acid content than adjacent areas most likely indicate positions of potential secondary constrictions, since most of these sites coincided with locations of faint constrictions that were detectable in the rye chromosomes when these were present in the intergeneric hybrid Elymus arenarius X Secale cereale. Factors such as the technique for chromosome preparations, degree of chromosome contraction, intensity of Feulgen coloration, chromosomal RNA cycle, nucleolar behavior during mitosis, and background effects may lead to inconsistencies in the photometric measurements.

Inhibition of serine/threonine-specific protein phosphatases causes premature activation of cdc2MsF kinase at G2/M transition and early mitotic microtubule organisation in alfalfa.

Reversible phosphorylation of serine/threonine residues of cell cycle-regulatory proteins is one of the key molecular mechanisms controlling eukaryotic cell division. In plants, the protein kinase partners (i.e. p34cdc2/CDC28-related kinases) have been extensively studied, while the role of counter-acting protein phosphatases is less well understood. We used endothall (ET) as a cell-permeable inhibitor of serine/threonine-specific protein phosphatases to alter cytological and biochemical characteristics of cell division in cultured alfalfa cells. A high concentration of ET (10 and 50 microM) inhibited both protein phosphatases 1 and 2 (PP1 and PP2A), while a low concentration (1 microM) of ET-treatment primarily reduced the PP2A activity. High concentrations of the inhibitor increased the frequency of hypercondensed early and late prophase chromosomes that could not enter metaphase. In contrast, a low concentration of ET did not interfere with chromosomal events but caused significant alterations in the organisation of microtubules. Exposure of cells to 1 microM ET resulted in disturbance of preprophase band formation, increase in the number of nuclei with prophase microtubule assembly, premature polarisation of the spindle, and abnormal phragmoplast maturation. Under the same conditions, the ET-treated cells exhibited an early increase in cdc2MsF kinase activity. These results suggest that PP2A contributes to the control of mitotic kinase activities and microtubule organisation. Normal chromosome condensation and mitotic progression are dependent on both PP1 and PP2A activities. The presented data support the functional role of protein phosphatases in the co-ordination of chromosomal and microtubule events in dividing plant cells.

Reorganization and condensation of chromatin in mitotic prophase nuclei of Allium cepa.

This paper studies the process and features of chromosome construction in mitotic prophase cells of Allium cepa. The results showed that a prominent reorganization of chromatin occurred during G2--early prophase. The 250-400 nm thick compact chromatin threads in G2 nuclei began to disorganize into about 30, 100 and 220 nm chromatin fibres which constituted the loosely organized chromosome outlines in early prophase before chromosome condensation. In middle prophase, chromosome condensation was characterized by the formation of many condensed regions (aggregates of chromatin), which increased in size (1-1.5 microns) when prophase proceeded. Meanwhile, the chromatin threads that constituted and connected the condensed regions became increasingly thicker (120-250 nm). In late prophase adjacent condensed regions fused to form cylinder-shaped chromosomes. Based on these observations, we come to the conclusion that the construction of prophase chromosomes is a two-step process, that is, the reorganization and condensation of chromatin. In addition, we report the study of silver-stained, DNA- and histone-depleted prophase chromosomes, describe morphological features of the non-histone protein (NHP) residue in early, middle and late prophase chromosomes, and discuss the roles of NHPs in chromosome construction.

C-banded karyotypes of Brassica campestris, B. oleracea, and B. napus

The chromosome complements of three Brassica species, namely B. campestris (2n = 20), B. oleracea (2n = 18), and B. napus (2n = 38), were studied using the air-dry method and C-banding. Karyotypes and ideograms of late prophase chromosomes were constructed, since contracted metaphase chromosomes were generally not suitable for this purpose. The three species generally had a similar banding pattern, manifested in the presence of a centromeric C-band in all chromosomes and heterochromatic knobs at the telomeric end of some chromosomes. The centromeric C-bands were more pronounced in B. campestris than in B. oleracea. Depending on the centromeric position, the chromosomes were grouped into median, submedian, subterminal, and terminal types. All chromosome pairs were morphologically distinguishable. Only one nucleolar chromosome pair, with heterochromatic satellites, was observed in each species. When compared, it was possible to distinguish chromosomes of both B. campestris and B. oleracea type in B. napus, but conclusive evidence as to the origin of all chromosome pairs in B. napus was not at hand.Key words: Brassica, chromosomes, late prophase, C-bands, knob structures, karyotypes, idiograms.

High resolution G-banding patterns of Syrian hamster chromosomes.

The late prophase, prometaphase, early metaphase, and metaphase chromosomes of Syrian hamster embryo fibroblast cells were G-banded using a technique combining actinomycin D pretreatment and Wright/Giemsa staining. Late prophase chromosomes have approximately twice as many bands as metaphase chromosomes, whereas prometaphase and early metaphase chromosomes have intermediate numbers of bands. An idiogram for metaphase and late prophase chromosomes is presented, and a nomenclatural system for identifying individual bands of Syrian hamster chromosomes is proposed.

G-banding patterns of high-resolution human chromosomes 6--22, X, and Y.

A precise schematic representation of the number, height, position, and staining intensity of the Giemsa bands of late prophase, prometaphase, early metaphase, and mid-metaphase chromosomes 6--22, X, and Y is presented. Late prophase chromosomes were found to have 2--2 1/2 times the length and 3--3 1/2 times the number of bands previously observed in mid-metaphase, whereas prometaphases and early metaphases were intermediate in length and number of bands. In this work, the maximum number of bands observed per haploid set in late prophase was 1353, while more than 350 were generally found in mid-metaphase.

A cytogenetic study of bipolar affective illness

Cytogenetic studies in psychiatry are important in view of the potential multiple etiologies of psychiatric syndromes, the strong genetic component of the functional psychoses, and the high incidence of chromosome abnormalities reported in diverse psychiatric populations. These studies, that suffered largely from heterogenous patient samples and lack of diagnostic criteria, involved mainly “gross” screening for sex chromosome defects (sex chromatin). As a result, the incidence of minor chromosome variants, as detected with new chromosome techniques, remains largely unknown in psychiatry. Bipolar affective disorder (manic-depressive) is a good place to start the more elaborate studies, since criteria for diagnosis is widely agreed upon and the illness has a predictable course and treatment response suggestive of a common etiology. Recent cytogenetic developments, such as the chromosome banding techniques, permit the exact identification of chromosomes through the differential staining of their segments. Evidence from the record of human chromosome imbalance indicates that banding patterns may also reflect the genetic constitution of a given chromosomal segment. The use of late prophase or early metaphase chromosomes instead of the customary midmetaphases considerably increases visual resolution. Late prophase chromosomes show over 1240 bands per haploid set, representing four times the number of bands observed on midmetaphase chromosomes. Since it is believed that man has approximately 30,000 genes per cell, the more elongated chromosomes would bring us relatively close to the gene level (around 23 genes per observed band) (Fig. 1). The present study was prompted by the observation of linkage of bipolar affective disorder to two genetically distant loci in the X chromosome in some informative families 2–4 and a recent report of familial X-linked mental retardation in connection with an X chromosome defect. 5 The latter highlights the potential importance of studying chromosome structure in X-linked disorders. We began “standard” chromosome studies on a homogenous sample of bipolar patients diagnosed according to research diagnostic criteria. Subsequently, studies of chromosome banding and analyses of X chromosome structure using elongated chromosomes (late prophase/early metaphase) were performed in selected cases.

On the spermatogonial divisions inAularches miliaris, L.

1. There are 19 telomitic rodshaped chromosomes inAularches. 2. The spermatogonial cells and the behaviour of the chromosomes in them are similar in general to the same processes in other grasshoppers. 3. There is strong evidence for the chromonema theory of the structure of chromosomes. 4. The chromonemata are double in the telophases and become very thin and reach the limit of visibility during the resting stage. This supports the observations of Robertson, McClung and others on the telophase splits in grasshoppers. 5. The chromosome vesicles are formed in the interphase due to the limited centrifugal movement of the chromosome matrices. 6. The chromonemata exhibit a spiral structure in the prophase. 7. The earliest prophase stages show the chromonemata to be double. 8. The chromonemata gradually thicken and uncoil leading to the late prophase chromosomes.