Location of the Nucleolus Organizer Regions on the Sex Chromosomes of the Banded Killifish, Fundulus diaphanus

Copeia ◽  
1979 ◽  
Vol 1979 (3) ◽  
pp. 544 ◽  
Author(s):  
W. Mike Howell ◽  
D. Ann Black
Keyword(s):  
Sex Chromosomes ◽  
Nucleolus Organizer ◽  
Nucleolus Organizer Regions ◽  
Banded Killifish ◽  
Fundulus Diaphanus

Karyotyping Melandrium album, a dioecious plant with heteromorphic sex chromosomes

Genome ◽  
1990 ◽  
Vol 33 (4) ◽  
pp. 556-562 ◽  
Author(s):  
D. D. Ciupercescu ◽  
J. Veuskens ◽  
A. Mouras ◽  
D. Ye ◽  
M. Briquet ◽  
...  
Keyword(s):  
In Situ Hybridization ◽  
Sex Chromosomes ◽  
Nucleolus Organizer ◽  
Rrna Genes ◽  
Hybridization Technique ◽  
Metaphase Chromosomes ◽  
Nucleolus Organizer Regions ◽  
Melandrium Album ◽  
Group B

Mitotic metaphase chromosomes of Melandrium album obtained from root protoplasts were studied. Morphologically, the chromosomes were either metacentrics or submetacentrics. They were classified into three distinct groups: group A comprising six pairs of autosomal metacentrics, group B comprising five pairs of autosomal submetacentrics, and the sex chromosomes: X and Y. The X chromosome is a metacentric (r = 1.44), which accounts for more than 14% of the genome. The Y chromosome is a metacentric with, virtually, equal arms (r = 1.09) and accounts for 21% of the genome, being the largest of the complement. The Y:X ratio was 1.4. Ethidium bromide, caffeine, and vinblastine were used to obtain a better resolution and higher frequency of satellited chromosomes 7q and 9p. The proposed karyotype of M. album is 2n = 24, XX, s(7q;9p) for female and 2n = 24, XY, s(7q;9p) for male plants. Nucleolus organizer regions (NORs) were present at the telomeric sites of three chromosome pairs: 7q, 9p, and 10p. The NORs were polymorphic, particularly between the nonhomologous chromosomes. The in situ hybridization technique localized the rRNA genes on four chromosome pairs: 5p, 7q, 9p, and 10p. The discrepancy between the NORs and the hybridization signals was probably due to the fact that NORs were restricted only to transcriptionally active rRNA genes. It was concluded that for a complete description and characterization of rRNA genes, both NOR detection and in situ hybridization techniques, as complementary methods, should be employed.Key words: Melandrium album, karyotype, satellites, idiogram, nucleolus organizer regions, in situ hybridization.

scholarly journals Evolutionary pattern of karyotypes and meiosis in pholcid spiders (Araneae: Pholcidae): implications for reconstructing chromosome evolution of araneomorph spiders

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Ivalú M. Ávila Herrera ◽  
Jiří Král ◽  
Markéta Pastuchová ◽  
Martin Forman ◽  
Jana Musilová ◽  
...  
Keyword(s):  
Sex Chromosomes ◽  
Chromosome Evolution ◽  
Karyotype Evolution ◽  
Sex Chromosome ◽  
Genomic Analysis ◽  
Nucleolus Organizer ◽  
Evolutionary Pattern ◽  
Holokinetic Chromosomes ◽  
Nucleolus Organizer Regions ◽  
The Family

Abstract Background Despite progress in genomic analysis of spiders, their chromosome evolution is not satisfactorily understood. Most information on spider chromosomes concerns the most diversified clade, entelegyne araneomorphs. Other clades are far less studied. Our study focused on haplogyne araneomorphs, which are remarkable for their unusual sex chromosome systems and for the co-evolution of sex chromosomes and nucleolus organizer regions (NORs); some haplogynes exhibit holokinetic chromosomes. To trace the karyotype evolution of haplogynes on the family level, we analysed the number and morphology of chromosomes, sex chromosomes, NORs, and meiosis in pholcids, which are among the most diverse haplogyne families. The evolution of spider NORs is largely unknown. Results Our study is based on an extensive set of species representing all major pholcid clades. Pholcids exhibit a low 2n and predominance of biarmed chromosomes, which are typical haplogyne features. Sex chromosomes and NOR patterns of pholcids are diversified. We revealed six sex chromosome systems in pholcids (X0, XY, X1X20, X1X2X30, X1X2Y, and X1X2X3X4Y). The number of NOR loci ranges from one to nine. In some clades, NORs are also found on sex chromosomes. Conclusions The evolution of cytogenetic characters was largely derived from character mapping on a recently published molecular phylogeny of the family. Based on an extensive set of species and mapping of their characters, numerous conclusions regarding the karyotype evolution of pholcids and spiders can be drawn. Our results suggest frequent autosome–autosome and autosome–sex chromosome rearrangements during pholcid evolution. Such events have previously been attributed to the reproductive isolation of species. The peculiar X1X2Y system is probably ancestral for haplogynes. Chromosomes of the X1X2Y system differ considerably in their pattern of evolution. In some pholcid clades, the X1X2Y system has transformed into the X1X20 or XY systems, and subsequently into the X0 system. The X1X2X30 system of Smeringopus pallidus probably arose from the X1X20 system by an X chromosome fission. The X1X2X3X4Y system of Kambiwa probably evolved from the X1X2Y system by integration of a chromosome pair. Nucleolus organizer regions have frequently expanded on sex chromosomes, most probably by ectopic recombination. Our data suggest the involvement of sex chromosome-linked NORs in achiasmatic pairing.

Synaptonemal complex analysis in spermatocytes of tilapia, Oreochromis niloticus (Pisces, Cichlidae)

Genome ◽  
1993 ◽  
Vol 36 (6) ◽  
pp. 1124-1128 ◽  
Author(s):  
Fausto Foresti ◽  
Claudio Oliveira ◽  
Pedro Manoel Galetti Junior ◽  
Lurdes Foresti de Almeida-Toledo
Keyword(s):  
Synaptonemal Complex ◽  
Sex Chromosomes ◽  
Oreochromis Niloticus ◽  
Complex Analysis ◽  
Sex Chromosome ◽  
Light And Electron Microscopy ◽  
Nucleolus Organizer ◽  
Nucleolus Organizer Regions ◽  
Synaptonemal Complex Analysis ◽  
Sex Chromosome System

Some adaptations of the synaptonemal complex (SC) whole-mounting technique first used in plants permitted its application to meiotic studies in tilapia, Oreochromis niloticus. Direct observation of the chromosome pairing process and bivalent structure during the meiotic prophase of this fish species by light and electron microscopy permitted the analysis of SCs in autosomes and the possible identification of sex chromosomes. The analysis of SCs in spermatocytes of O. niloticus revealed that all 22 bivalent chromosomes completely paired, except for the occurrence of a size heteromorphism in the terminal region of the largest bivalent associated with the presence of an incompletely paired segment during the synapsis process, which may be the cytological visualization of an XX/XY sex chromosome system in this species.Key words: fish cytogenetics, synaptonemal complex, fish meiosis, sex chromosomes, nucleolus organizer regions.

Polymorphism of interphase nucleolus organizer regions in imported pigs and their offspring

2014 ◽  
Vol 40 (3) ◽  
pp. 211-213
Author(s):  
S. K. Buteeva ◽  
M. L. Kochneva ◽  
K. V. Zhuchaev ◽  
S. V. Papshev
Keyword(s):  
Nucleolus Organizer ◽  
Nucleolus Organizer Regions

Age-related influence of piracetam on mitotic index and number of silver-stained nucleolus organizer regions

1992 ◽  
Vol 14 (2) ◽  
pp. 213-220 ◽  
Author(s):  
Walter Vormittag ◽  
Christian Ensinger ◽  
Leo Lesnjakovic ◽  
Scheiber Viktor
Keyword(s):  
Mitotic Index ◽  
Nucleolus Organizer ◽  
Nucleolus Organizer Regions ◽  
Age Related
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