جستجوی مقالات مرتبط با کلیدواژه "cytogenetic" در نشریات گروه "زیست شناسی"

Siamese fighting fish (Betta splendens) is originated from Southeast Asia and one of Indonesia’s most profitable exports commodity. However, scientific studies on Siamese fighting fish chromosomes remain limited. Chromosomal information is very useful for disclosing the diversity and genetic relationships of animals and provides clues to the most appropriate conservation measures for a species. Moreover, affordable chromosome visualization procedures are also a main concern for animal research. This research aims to determine the optimal chromosome preparation time, the best method for observing prometaphase, and the chromosomal characteristics of different types of betta fish based on their diploid numbers. The results showed that the optimal time for chromosome preparation is between 07:00 am and 12:00 pm and that the best method for observing chromosomes is the splash method from Kligerman and Bloom modified by soaking samples in colchicine for 11-12 h. The chromosome numbers of Giant, Plakat, Crown tail, and Halfmoon bettas are identical, i.e., 2n=42.

The red-orange-colored stigmas of saffron are one of the most expensive spices in the world. Meiosis processes in saffron showed that Crocus sativus L. is an autotriploid species with 2n=3x=8+8+8=24 chromosomes. The results obtained from the meiosis behavior indicated that the major role in the sterility of saffron is autotriploidy in this crop. Arrangement of chromosomes as trivalents in meiosis and formation of these trivalents in the forms of frying pan, chain type, Y type, V type, and triangle type at metaphase I, causes their imbalance junction at anaphase I. Unbalance disjunction of chromosomes at anaphase I and II with the occurrence of the lagging chromosomes in these phases, causes sterile gametes. Also, the formation of chromatid bridges at anaphase I and II with the occurrence of micronuclei at telophase II and tetrad stage are the other reasons for the sterility.

Karyomorphological study was carried out on 11 accessions from 6 sections belonging to 7 species of Astragalus growing in Iran. Chromosome numbers and karyotypes of two species (A. cephalanthus DC. and A. jacobsii Podlech) are new records. Two ploidy levels 2n = 2x = 16 and 2n = 4x = 32 were determined, the chromosomes size varied from 2.51 in A. cyclophyllos to 3.79 μm in A. fasciculifolius Boiss. in two accessions of A. cyclophyllos , a single pair satellite chromosomes were observed.

In this study, karyotypes of five Fritillaria species including F. avromanica, F. assyriaca, F. chlorantha, F. persica and F. raddeana belonging to three subgenera are presented. All species were diploid (2n = 2x = 24) with mean chromosome length of 15.86 µm. Four chromosome types (‘‘m’’, ‘‘sm’’, ‘‘st’’, ‘‘T’’) made five different karyotypic formula. Chromosome count of F. avromanica (2n = 2x = 24) is a new report. Analysis of variance for eight chromosomal parameters revealed inter specific chromosomal variation. Based on different karyotype asymmetry indices including TF %, CV %, A2, AI, AsK %, S%, F. assyriaca had the most asymmetrical karyotype. Based on Fluorescence in situ hybridization result, 4 and 6, 35S rDNA loci were observed for F. raddeana and F. persica respectively, which mainly located at distal or telomeric regions of chromosomes.

TheKaryotype and meiotic studies are investigated in 17 populations of four Clypeola species growing in Iran for the first time. The species studied showed 2n=2x=14 for C. lappacea and C. dichotoma while C. aspera and C. jonthlaspi were tetraploids. For C. aspera 2n=4x=26 & 24 and for C. jonthlaspi 2n=4x=32 were counted، supporting the published reports on C. jonthlaspi، C. lappacea، C. dichotoma and C. aspera. The karyotypic study was performed for C. aspera and C. lappacea. The chromosomes in these species were mainly metacentric and sub-metacentric. Mixoploidy and polysomaty has been observed in C. aspera populations. Meiosis studies were performed on 6 populations of three species of Clypeola. Chromosome number of n=16 for C. jonthlaspi، n=12 & 13 for C. aspera and n=7& 8 for C. lappacea were observed. Disploidy was observed in C. aspera and C. lappacea. Desynapsis and B chromosome are present in C. lappacea. Unreduced pollen grains were observed in three species.

Chromosome numbers were determined for the first time for 2 native species of Iran. The samples were collected from natural habitats. Paronychia kurdica (2n=18) of Caryophyllaceae family and Salsola yazdiana(2n=18) of Chenopodiaceae family were examined in this study. Ideograms were depicted for each species. Both of them had metacentric chromosomes.

Karyotypic observations showedthat 4 speciesincludingO.scorbiculata, O.melanotricha, O.aucherisubsp. teheranicaand O.oxypterahave 2n=16 chromosomes and according to the basic number of x=8, they are diploids. O.oxypterahas got the least total length (31.07) and average chromosome length (3.88) but the most TF% of 36.43% whichrefers to itsmostasymmetricalkaryotype. The karyotypescanbedivided as lA(O. scorbiculataand O.melanotricha), 1B (O.aucherisubsp. teheranica) and 2B (O.oxyptera) due to Stebbins classification.