Human Meiotic Chromosomes Research Articles

Chromomeric pattern of maize pachytene chromosomes after trypsin treatment.

The bivalent chromomeres of maize were analyzed by means of enzymatic treatment with trypsin. The aim was to verify if the effect of swelling observed in human meiotic chromosomes also occurs in these bivalents, and if this morphological change allows a greater visual resolution of the chromomeric pattern. Bivalents treated with trypsin showed a structure with sequential and linear distribution of small rings. Comparisons between bivalent morphology, treated and non-treated, indicated a collinearity among the sequences of rings and the chromomeres. The results obtained were considered useful to analyze and to make a chromomere map. This treatment can also provide cytological evidence that may help to understand the pairing process. It was concluded that the ring-shape was caused by trypsin-induced "disjoining" just in the chromomeric but not in the interchromomeric regions.

Imaging of human meiotic chromosomes by scanning near-field optical microscopy (SNOM)

Centromeres and telomeres are key structures of mitotic and meiotic chromosomes. Especially telomeres develop particular structural properties at meiosis. Here, we investigated the feasibility of scanning near-field optical microscopy (SNOM) for light-microscopic imaging of meiotic telomeres in the sub-hundred nanometer resolution regime. SNOM was applied to visualise the synaptonemal complex (SC) and telomere proteins (TRF1, TRF2) after differential immuno-fluorescent labelling. We tested and compared two different preparation protocols for their applicability in a SNOM setting using micro-fabricated silicon nitride aperture tips. Protocol I consisted of differential labelling of meiotic chromosome cores (SC) by SCP3 immuno-fluorescence and telomeres by TRF1 or TRF2 immuno-fluorescence, while protocol II combined absorption labelling with alkaline phosphatase substrates of cores with fluorescent labelling of telomeres. The results obtained indicate that protocol I reveals a better visualisation of structural (topographic) details than protocol II. By means of SNOM, meiotic chromosome cores could be visualised at a resolution overtopping that of far-field light microscopy.

ISCN Rules for Listing Chromosomal Rearrangements

It contains the standard system for numbering human chromosomes and constitutional rearrangements and the banding pattern for normal chromosomes at 400-, 550-, and 850-band levels of resolution. ISCN 1995 also contains guidelines for cancer cytogenetics and for in situ hybridization. The complete ISCN 1995 also contains nomenclature for human meiotic chromosomes (not included here). The guidelines presented herein are recommended for use when reporting karyotypes, designating chromosome rearrangements and aberrations, and indicating regions of the genome where DNA sequences are located. It contains the standard system for numbering human chromosomes and constitutional rearrangements and the banding pattern for.

Precise in situ localization of NCAM, ETS1, and D11S29 on human meiotic chromosomes.

In order to sublocalize NCAM, ETS1, and the anonymous DNA fragment D11S29 within 11q23, in situ hybridization was performed on pachytene bivalents. Analysis of the grain distribution within the band 11q23 indicated that the chromosomal sublocalization of both NCAM and D11S29 was in 11q23.1, whereas ETS1 was found to be localized in 11q23.3. These results clearly demonstrate the usefulness of in situ hybridization applied to pachytene bivalents to obtain accurate gene sublocalization.

DNase I hypersensitive sites along the XY bivalent at meiosis in man include the XpYp pairing region.

The DNase I nick translation technique has been applied to human meiotic chromosomes in situ. At metaphase I, distinct hot spots of autoradiographic labelling occur at three positions along the XY bivalent; over the Xpter and Ypter pairing tips, over Xq and Yq terminal/telomeric segments, and at a site just below the centromere in Xq. The latter might correspond to the postulated human inactivation centre. Compared with somatic chromosomes, human meiotic bivalents in general exhibit a greater accessibility to DNase I. Site-specific conformational changes in the DNA between somatic and germ line cells could be a necessary prerequisite for crossing-over.

Preliminary study of stages of human meiosis in spermatocytes and ovocytes (author's transl)

Human meiotic chromosomes, from spermatocytes and ovocytes, are described after observations of whole mount preparations under E.M. Small testicular and ovarian fragments are put in distillated water, then macerated; the cell suspension is spread on the surface of sheet copper grids covered with formvar plus collodion films. After dehydratation interesting stages are selected under L.M. before observations under E.M. Zygotene and pachytene are the most common stages. During pachytene the chromomeres are well individualized; the synaptonemal complex may be observed; chromatin fibers connect the chromosomes to nuclear pores, interchromosomal fibers joint the bivalents. Zygotene and pachytene bivalents are very similar in the male and the feminine germ cells.

Cytogenetic aspects of human male meiosis.

During the first half of the present century human meiotic chromosomes were studied mainly in order to obtain information on the chromosome number of man. Different authors came to different conclusions regarding this number due to the fact that the only technique available for such studies was the use of histological sections from fixed testicular material, which does not give adequate spreading of the chromosomes (see, e.g., reviews by Kjessler81 and Hamerton55). In 1952 Mittwoch,103 using squash preparations, reported that there were 24 bivalents in primary spermatocytes from a subject with Down’s syndrome. These results were at that time believed to support the opinion that the normal chromosome number of man was 48, and mongoloid patients were therefore believed to have a normal chromosome constitution. The definite demonstration that there are 23 bivalents in normal human primary spermatocytes came in 1956, when Ford and Hamerton41 introduced hypotonic pretreatment of the testicular material before squashing. The mean chiasma count was found to be 55.9 (range 50–63), and on the basis of this result the total length of the human genome was estimated to be 27.9 morgans. The finding of 23 bivalents constituted an immediate confirmation of the observation made by Tjio and Levan143 on somatic cells that man has 46 chromosomes.KeywordsSynaptonemal ComplexMeiotic ChromosomeSecondary ConstrictionPrimary SpermatocyteRobertsonian TranslocationThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Whole mount electron microscopy of human meiotic chromosomes

Human meiotic chromosomes were examined by whole mount electron microscopy. The synapsed bivalents and synaptonemal complex in pachytene cells were readily visualized. The chromatin fibers attach to the lateral element of the synaptonemal complex and radiate laterally. When the water spread cells were treated with DNase the chromatin could be washed away leaving intact the proteinaceous synaptonemal complex, including the central element. This technique may be of value in studying individuals with translocation chromosomes.

Meiotic chromosomes of man.

AbstractA study of human meiotic chromosomes led to a classification of the bivalents according to their dimension, general characteristics and chiasma frequency. Particular attention was paid to the X and Y chromosomes. The consistency of pattern shapes in individual chromosomes at diakinesis indicated the potential for karyotyping the meiotic chromosomes of man.

STUDIES ON HUMAN MEIOTIC CHROMOSOMES FROM TESTICULAR TISSUE

STUDIES ON HUMAN MEIOTIC CHROMOSOMES FROM TESTICULAR TISSUE