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1

Differentiation of generative organs in dioecious species

100%
Dastych W., Zenkteler E.
Biotechnologia
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2010
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issue 2
38-56
EN
Flowering plants are mostly hermaphroditic (i.e. bear both stamens and pistils). In the course of evolution such progenitors have repeatedly given rise to species with separate male and female individuals. Plants display a great variety of sexual systems that could be reduced to three types: 1) the two sexes occurring on separate plant; 2) both sexes occurring in the same individual; 3) a combination of the former possibilities. Gender is determined by genotype, but the mechanisms of determination are extremely diverse among species. The determinants of sexual phenotype range from sex chromosomes (Silene latifolia), through hormonal regulation (in Cucumis sativa), to pheromonal contacts (between fern gametophytes). Salix viminalis, as a dioecious species, revealed sexual dimorphism (occurring in a flowering stage). In their breeding as a short-rotation energy crop, an early determination of sex would be necessary to remove, for agronomic reasons, the male plants. Within Salicaceae a multi-locus sex determination system is the main model of sexual differentiation. Despite the fact that a great progress has been achieved in identification of genes that regulate sex expression, future efforts will be necessary to recognize these processes at the molecular level.
2

Karyotypes, sex chromosome systems, and male meiosis in Finnish psyllids (Homoptera, Psylloidea)

100%
Kuznestsova V. G., Nokkala S., Maryanska-Nadachowska A.
Folia Biologica
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1997
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vol. 45
143-152
EN
The karyotypes and structure of the testes were studied in 12 species of Psylloidea belonging to the families Aphalaridae, Psyllidae and Triozidae. Males of ten species, namely Aphalara avicularis Oss., A. rumicicola Klimasz., Camaratoscena speciosa (Flor), Cacopsylla ambiqua Frst., C. peregrina Frst., Bactericera curvatinervis Frst., B. striola Flor., Trioza anthrisci Burckhardt, and T. apicalis Frst. have two seminal follicles per testis, this being the most typical testis structure in Psylloidea. Males of Psylla betulaenanae Oss. and P. ledi Flor. were found to display 4 follicles per testis. Ten species share 2n=24+X0 in males, which is the basic karyotype in Psylloidea as a whole, whereas Bactericera curvatinervis Frst. and B. striola Flor. have 2n=24+neo-XY. In some karyotypes, one B-chromosome was found. Its peculiar behaviour during some stages of the first meiotic division was examined. The karyotype of A. rumicicola was studied after Giemsa C-banding. Using C-band in an autosome pair as the marker of one of the telomeres it was proved that holokinetic chromosomes of psyllids are in fact dikinetic in the first meiotic division.
3

Cytogenetic markers for X chromosome in a karyotype of rainbow trout from Rutki strain (Poland)

100%
Ocalewicz K.
Folia Biologica
|
2002
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vol. 50
|
issue 1-2
13-16
EN
Cytogenetic or molecular identification of sex chromosomes could help in breeding studies in producing monosex fish stocks, estimating success of androgenesis, gynogenesis, etc. Among fish species sex chromosomes are recognizable in only a few cases. Some populations of rainbow trout Oncorhynchus mykiss show morphologically differentiated sex chromosomes. A strain from Rutki, Poland, showed a heteromorphic pair of subtelocentric chromosome: presumably of the XY type in the male and XX in the female. Restriction endonuclease and DAPI banding resulted in a characteristic banding pattern enabling identification of the X chromosome.
4

Chromosome rearrangements and survival of androgenetic rainbow trout (Oncorhynchus mykiss)

88%
Ocalewicz K., Dobosz S., Kuzminski H., Nowosad J., Goryczko K.
Journal of Applied Genetics
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2010
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vol. 51
|
issue 3
309-317
EN
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.
5

First evidence of sex chromosome pre-reduction in male meiosis in the Miridae bugs (Heteroptera)

75%
Grozeva S., Nokkala S., Simov N.
Folia Biologica
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2006
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vol. 54
|
issue 1-2
9-12
EN
The karyotype and male meiosis of Macrolophus costalis Fieber (Insecta, Heteroptera, Miridae) were studied using C-banding, AgNOR-banding and DNA sequence specific fluorochrome staining. The chromosome formula of the species is 2n=28(24+X1X2X3Y). Male meiotic prophase is characterized by a prominent condensation stage. At this stage, two sex chromosomes, 'X' and Y are positively heteropycnotic and always appeared together, while in autosomal bivalents homologous chromosomes were aligned side by side along their entire length, that is, meiosis is achiasmatic. At metaphase I, 'X' and Y form a pseudobivalent and orient to the opposite poles. At early anaphase I, the 'X' chromosome disintegrates into three separate small chromosomes, X1, X2, and X3. Hence both the autosomes and sex chromosomes segregate reductionally in the first anaphase, and separate equationally in the second anaphase. This is the first evidence of sex chromosome pre-reduction in the family Miridae. Data on C-heterochromatin distribution and its composition in the chromosomes of this species are discussed.
6

The behaviour of a multiple sex chromosome system in Dundocoris flavilineatus (Heteroptera: Aradidae: Carventinae) that originated by autosome-sex chromosome fusion

75%
Jacobs D. H.
|
|
vol. 51
|
issue 1-2
23-32
EN
The nominate subspecies of Dundocoris flavilineatus Jacobs occurs in indigenous evergreen forests over a wide area in KwaZulu-Natal and the Eastern Cape Province of South Africa. It has a chromosome number of 2n = 28XY, which is the ancestral number for the genus. D. flavilineatus ndabeniensis, which comprises an isolated sibling population at Ndabeni forest in northern KwaZulu-Natal, possesses a multiple sex chromosome system, presumably a X1X2Y system and has a chromosome number of 2n = 27X1X2Y. The system probably originated when an autosome and the Y-chromosome of the 28XY karyotype fused. In contrast to the situation previously described in the XY1Y2 system of D. nodulicarinus the autosomal and original Y-chromosome parts of the neo-Y chromosome seem to have a reciprocal influence on each other in terms of structure and staining intensity during prophase I. The autosomal part of the neo-Y adopts a granulate, heteropycnotic, linear structure while the original Y part is less globular than usual in structure. The neo-X chromosome (= X2) behaves like, and stays isopycnotic with the autosomes. It is connected to the neo-Y by terminal association ? probably a terminal chiasma. The sex chromosome system is post-reductional and a sex chromosome trivalent is present in all metaphase II cells. The origin and behaviour of the neo-X1X2Y sex chromosome system in D. flavilineatus ndabeniensis are described, discussed, illustrated with photomicrographs and compared to the XY1Y2 system in D. nodulicarinus. Idiograms of the karyotypes of the two subspecies of D. flavilineatus are also presented.
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