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We analysed chromosome lengths, karyotype structure, and nuclear DNA content (flow cytometry) in diploid (2n=20) and triploid (2n=30) European H. lupulus var. lupulus, American H. lupulus var. neomexicanus (2n=20) and Japanese ornamental hop, H. japonicus (F/2n=16; M/2n=17). Diploid female representatives of H. lupulus var. lupulus and H. l. var. neomexicanus differed in total length of the basal chromosome set (23.16 µm and 25.99 µm, respectively) and nuclear 2C DNA amount (5.598 pg and 6.064 pg) but showed similar karyotype structure. No deviation from the additivity, both in chromosome length and 2C DNA amount was evidenced in triploid monoecious H. lupulus (2n=30, XXY). H. japonicus showed different karyotype structure, smaller basal chromosome set (F/18.04 µm, M/20.66 µm) and lower nuclear DNA amount (F/3.208 pg and M/3.522 pg). There are first evaluations of nuclear genome size in diploid, not commercial representative of European H. lupulus var. lupulus and American H. lupulus var. neomexicanus and first attempt to determine the absolute male and female genome size in two Humulus species.
The electrophoretic polymorphism of blood proteins, and karyotypes, were studied in up to 33 captive-bred Persian goitred gazelles Gazella s. subgutturosa (Giildenstaedt, 1780). Allozymes, haemoglobins and serum proteins representing 33 putative genetic loci displayed four biallelic polymorphisms (carbonic anhydrase, malate dehydrogenase, mannose phosphate isomerase, transferrin), resulting in a percentage polymorphism of p = 0.121, and an expected heterozygosity of He = 0.047. Six males had 2n = 31, and seven females 2n = 30 chromosomes. This sex-specific difference was due to an X-autosomal translocation, coupled with a XYiYz sex determining system in males. Neither karyotypes nor protein polymorphism provided evidence to explain the high mortality of newborn goitred gazelles.
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Sex-ratio bias in seeds of dioecious Rumex species with sex chromosomes is an interesting and still unsettled issue. To resolve gender among seeds of R. acetosa and R. thyrsiflorus (two species with an XX/XY1Y2 sex chromosome system), this work applied a PCR-based method involving DNA markers located on Y chromosomes. Both species showed female-biased primary sex ratios, with female bias greater in R. acetosa than in R. thyrsiflorus. The observed predominance of female seeds is consistent with the view that the female biased sex ratios in Rumex are conditioned not only postzygotically but also prezygotically
The field vole (Microtus agrestis) is characterised by extremely large blocks of heterochromatin on both the X and Y chromosome. Some other Microtus also have blocks of heterochromatin on their sex chromosomes but not as extensive and always of independent origin from the heterochromatic expansion found in M. agrestis. Coupled with evidence of geographic variation in large heterochromatic blocks within other species (e.g. in the western hedgehog Erinaceus europaeus), it might be expected that field voles would show substantial variation in size and disposition of the sex chromosome heterochromatin. In fact, only minor variation has been described up to now. Those studies conducted previously were largely on field voles from central and northern Europe. Here, we describe the karyotype of field voles from Portugal, of interest because recent molecular studies have shown field voles from western Iberia to be a separate evolutionary unit that might be considered a cryptic species, distinct from populations further to the east. The two Portuguese field voles (one female, one male) that we examined also had essentially the same karyotype as seen in other field voles, including the giant sex chromosomes, but with small differences in the structure of the Y chromosome from that described previously. The finding that field voles throughout Europe show relatively little variation in their giant sex chromosomes is consistent with molecular data which suggest a recent origin for this complex of species/near-species.
The purpose of this work was to quantify the impact of spontaneous and X-radiation-induced chromosome rearrangements on survival rate of androgenetic rainbow trout (Oncorhynchus mykiss). Various doses of X irradiation (50, 150, 250, 350 Gy) were used for inactivation of nuclear DNA in oocytes. After the irradiation, eggs were inseminated with normal sperm from 4 males derived from a strain characterized by Robertsonian rearrangements and length polymorphism of the Y chromosome. The haploid zygotes were exposed to a high hydrostatic pressure (7000 psi) to duplicate the paternal DNA. Neither Robertsonian chromosome polymorphism nor the Y chromosome morphology impaired the viability of the androgenetic embryos and alevins. Moreover, survival of eyed embryos of the androgenetic rainbow trout increased significantly with increasing doses of oocyte X irradiation. After 6 months of rearing, only specimens from the 250 and 350 Gy variants survived. The number of fingerlings with remnants of the maternal genome in the forms of chromosome fragments was higher in the 250 Gy group. Intraindividual variation of chromosome fragment number was observed, and some individuals exhibited haploid/diploid mosaicism and body malformations. Individuals irradiated with less than 250 Gy died, presumably because of the conflict between intact paternally derived chromosomes and the residues of maternal genome in the form of chromosome fragments.
The present study describes a rapid, simple method of bovine IVF embryo sexing by use of PCR technique. A pair of primers corresponding to the bovine amelogenin sequence has been used. The Rapid Cycler (Idaho Technology, USA) used in the current experiment enabled the PCR programme consisting of 55 cycles to be completed in less than 40 minutes. Therefore the total sexing procedure could be performed in less than 90 minutes. The described method succeded in case of 85% analysed embryos.
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