Search results for "Ploidy"
showing 10 items of 299 documents
Chromosomal studies of five tropical scorpaeniform fishes (Teleostei, Scorpaenidae)
2003
Abstract The karyotypes of five species of Scorpaenidae (genera Scorpenopsis, Dendrochirus and Pterois) from the Indian Ocean were analysed using various banding methods and in situ hybridisation with a ribosomal probe. All the species investigated are characterised by a diploid set of 48 chromosomes (mainly acrocentric and/or subtelocentric) and by a NOR location on the small arm of a medium‐sized pair. All the chromosomes stained uniformly with DAPI, whereas C‐banding evidenced a small amount of hete‐rochromatin. Despite the marked morphological differences among these species, the low degree of diversification of the chromosome sets with respect to the ancestral set of teleosts (2n = 48 …
Cell cycle: Aetiology of age-associated aneuploidy: a mechanism based on the 'free radical theory of ageing'
1995
A general model is put forward to explain the mechanism by which age-associated aneuploidies are produced. This is based on the free radical theory of ageing, which assumes a rise in oxidative stress with age. It is proposed that determination of indicators of oxidative stress in oocytes from various sources could be a first step in the testing of this hypothesis.
Genetische Untersuchungen zur Inkompatibilität im Culex-pipiens-Komplex
1970
In crosses between populations of the mosquito Culex pipiens of different geographical origin three crossing types have been found (1) crosses with normal offspring (2) crosses with reduced offspring and (3) crosses that show almost total incompatibility. In the case of incompatible crosses 99.9% of the developing embryos are lethal and only about 0.1% of the embryos hatch and develop into fertile diploid females. The origin of the exceptional diploid females has been investigated by means of the marker genes Kuf, r, w, var, y and ru. These females develop from a diploid oocyte or from a diploid nucleus that originated by fusion of the pronucleus and the last polar body. This has been concl…
Characterization of mitotic and meiotic, chromosomes of the vermetid gastropodDendropoma (Novastoa) Petraeum(Monterosato, 1884) (Mollusca, Caenogastr…
1997
Abstract The vermetid gastropod Dendropoma (Novastoa) petraeum from the Northwestern coast of Sicily was investigated karyologically. The count of spermatocyte bivalents at diakinesis gave the haploid number of this species as n=17. The count of mitotic chromosomes in males, females and early developing embryos gave the diploid number as 2n=34. Irrespective of sex, the karyotype of D. petraeum consists of 17 homomorphic chromosome pairs, of which 8 are metacentric, 4 subtelocentric and 5 acrocentric. This species is characterized by the presence of two chromosomes per cell involved in nucleolus organization (NOR) and by a low amount of constitutive heterochromatin.
Intra-allelic variation in introns of the S13-RNase allele distinguishes sweet, wild and sour cherries
2010
The cherry (Prunus avium), a self-incompatible diploid species, and the sour cherry (Prunus cerasus), a self-incompatible or self-compatible allotetraploid species derived from P. avium and Prunus fruticosa, share several S-RNase alleles, including S13. An inactive form, S13° ,i s found in some sour cherries. Two (AT) microsatellites are associated with allele S13-RNase, one in the first intron and one in the second. Their length polymorphisms were studied in 14 sweet and 17 wild cherries (both P. avium) and in 42 sour cherries. Fluorescent primers amplifying each microsatellite were designed and amplification prod- ucts sized on an automated sequencer. Variants ranged from 247 to 273 bp fo…
Spermatocyte chromosome analysis of the slugLehmannia melitensis(Lessona and Pollonera, 1891) (Mollusca, Pulmonata) using conventional, NOR- and C-ba…
1993
SUMMARYDiploid number 2n = 40 and haploid number n = 20 for the slug Lehmannia melitensis have been determined. These chromosome values being considerably different from those reported for slugs belonging to other limacid genera support the notion that the genus Lehmannia is particular within the family Limacidae. Nucleolus organizer regions (NORs) and C-banding pattern of L. melitensis are described.
Cytogenetic characterization ofBrachidontes pharaonis(Fisher P., 1870): Karyotype, banding and fluorescentin situhybridization (fish) (Mollusca: Biva…
2000
Abstract The mussel Brachidontes pharaonis (Fisher P., 1870) (Bivalvia: Mytilidae) has a diploid chromosomal set of 28 made up of 14 pairs of which eight are mono-armed (ST) and six bi-armed (M+SM). Fourteen bivalents occur in spermatocytes both at pachytene and metaphase-I. The use of combined silver and CMA3 staining reveals that nucleolus organizer regions (NORs) are located terminally on the long arm of a small subtelocentric chromosome pair (pair 14) and are compartmentalized in GC base pairs. A Paracentrotus lividus (Echinodermata) 4.3 kilobase (kb) rDNA probe (prR14) consisting of sequences from the 3′ end of 18S rDNA to the 3′ end of 26S rDNA was used to map the rDNA loci of B. phar…
Aneuploidy and Ethanol Tolerance in
2018
Response to environmental stresses is a key factor for microbial organism growth. One of the major stresses for yeasts in fermentative environments is ethanol. Saccharomyces cerevisiae is the most tolerant species in its genus, but intraspecific ethanol-tolerance variation exists. Although, much effort has been done in the last years to discover evolutionary paths to improve ethanol tolerance, this phenotype is still hardly understood. Here, we selected five strains with different ethanol tolerances, and used comparative genomics to determine the main factors that can explain these phenotypic differences. Surprisingly, the main genomic feature, shared only by the highest ethanol-tolerant st…
Genetic diversity of Iberian populations ofBemisia tabaci(Hemiptera: Aleyrodidae) based on random amplified polymorphic DNA-polymerase chain reaction
2001
The genetic structure of six Iberian populations of the whitefly Bemisia tabaci, two of them biotype Q, one biotype B, and the other three a mixture of both, has been studied using random amplified polymorphic DNA-polymerase chain reaction (RAPD-PCR). A total of 336 individuals was completely discriminated by means of 234 scored bands. Separate analyses of molecular variance of haploid males and diploid females using the pairwise number of differences between haplotypes showed that biotypes contribute significantly more to the observed variability than populations within biotypes. On average, gene flow between two biotypes of the same population is lower than between populations of identica…
Microsporogenesis in three wild species of the genusAntirrhinumL. (A. litigiosumPau,A. pulverulenthumLazaro andA. subbaeticumGüemes, Sánchez and Mate…
2010
The diploid chromosome number (2n = 2x = 16) in three wild species A. litigiosum Pau, A. pul- verulenthum Lazaro and A. subbaeticum Guemes, Sanchez & Mateu, belonging to the genus Antirrhinum was cytologically observed. Genetic stability of the simultaneous meiotic division type was found in these natural growing snapdragons. The synchronicity at the initial meiotic stages and at tetrad and pollen creation was high and disappeared with the diakinesis initiation. Refl ecting the systematic position of the studied species into Antirrhinum, the performed investigation mani- fested similarity: in the presence of univalents and quadrivalent confi gurations parallel with bivalents at the early me…