introduction: heterochromatin consists of dna sequences that are not transcribed, and are repeated in short tandem at heterochromatic regions of chromosomes 1, 9, 16 as well as the distal part of long arm of chromosome y. slightly large tandem repeats at the centromeres of human chromosomes are also considered as heterochromatin regions. the main aim of the present study is to evaluate the hete...

background: high-energy ionizing radiation is harmful and changes the genetic makeup of dna, which can lead to increased risk of cancer. thus, the exposure of radiation dose should be under control and limited. ionizing radiation might lead to some chromosome aberrations like dicentric. there is a strong relation between the frequency of dicentric chromosome in metaphase, and the received dose....

eight accessions of thyme medicinal plant, belonging to iranian endemic thymus daënensis, t. eriocalyx, t. migricus and an unknown thymus spp species, were tested for karyotypic analysis, using squash technique and 2% (w/v) aceto-orcein staining method. chromosomal parameters examined were: short arm (s), long arm (l), total length of chromosome (tl), arm ratio (ar), r-value, total chromosome v...

In order to analyze chromosome numbers and karyotypes of intestinal trematodes belonging to the genus, Metagonimus, the gonad tissues of M. takahashii, M. miyatai, and M. yokogawai were prepared and examined. The number of bivalents in the first meiotic division of M. takahashii was nine (n = 9). The diploid number of M. miyatai was observed to be eighteen (2n = 18) and their chromosomes consis...

In most eukaryotes, centromeres assemble at a single location per chromosome. Naturally occurring telocentric chromosomes (telosomes) with a terminal centromere are rare but do exist. Telosomes arise through misdivision of centromeres in normal chromosomes, and their cytological stability depends on the structure of their kinetochores. The instability of telosomes may be attributed to the relat...

in order to determine the cytotypes of 67 accessions of aegilops crassa from iran, two flow cytometry and cytogenetics methods were applied. the nucleus of the young leaves was colored using dapi and the intensity of fluorescent determined by flow cytometry. by comparing the intensity of the fluorescent of the ae. crassa samples with ae. tauschii (as an standard sample), two cytotypes 4x and 6x...