The Karyotype of Blainville’s Beaked Whale, Mesoplodon densirostris

2020 ◽  
pp. 1-6
Author(s):  
Ross Brookwell ◽  
Kimberly Finlayson ◽  
Jason P. van de Merwe
Keyword(s):  
Chromosome Number ◽  
Y Chromosome ◽  
X Chromosome ◽  
Organizer Region ◽  
Nucleolar Organizer Region ◽  
Nucleolar Organizer ◽  
Large Block ◽  
Beaked Whale

The karyotype of the Odontocete whale, <i>Mesoplodon densirostris</i>, has not been previously reported. The chromosome number is determined to be 2n = 42, and the karyotype is presented using G-, C-, and nucleolar organizer region (NOR) banding. The findings include NOR regions on 2 chromosomes, regions of heterochromatic variation, a large block of heterochromatin on the X chromosome, and a relatively large Y chromosome. The karyotype is compared to published karyograms of 2 other species of <i>Mesoplodon</i>.

X-chromosome replication patterns in adult, newborn and prenatal opossums

1994 ◽  
Vol 6 (4) ◽  
pp. 533 ◽  
Author(s):  
ES Robinson ◽  
PB Samollow ◽  
JL VandeBerg ◽  
PG Johnston
Keyword(s):  
X Chromosome ◽  
Developmental Stages ◽  
Organizer Region ◽  
Nucleolar Organizer Region ◽  
Chromosome Complement ◽  
Nucleolar Organizer ◽  
Chromosome Replication ◽  
Monodelphis Domestica ◽  
Molecular Techniques ◽  
Didelphis Virginiana

Somatic cells from the opossums Monodelphis domestica and Didelphis virginiana were labelled with 5-bromodeoxyuridine (BrdU), treated with colchicine, stained with acridine orange and examined using fluorescence microscopy. BrdU-incorporated metaphase spreads from females of M. domestica at developmental stages from late bilaminar blastocysts to adults showed replication asynchrony of the two (acrocentric) X chromosomes. The long arm of one X chromosome was the latest replicating region in the entire chromosome complement and is presumed to represent transcriptional inactivation and X dosage compensation. The minute short arm of the same X, which contains a nucleolar organizer region, was earlier replicating and synchronous with the short arm of its homologue and is thus assumed to escape inactivation. BrdU-incorporated spreads from cells of fetuses, neonates and adults of D. virginiana also showed a late replicating (submetacentric) X chromosome. The pattern was different from that of M. domestica because of the different morphology and the presence of large blocks of constitutive heterochromatin in both homologues. The timing and pattern of replication of the single X in males of both species resembled the earlier replicating X in females. The array of molecular techniques now available offers the best means for investigating X-chromosome replication and activity states of X-linked genes in the earliest stages of marsupial embryogenesis.

Studies of the X chromosome of Anopheles albimanus

1985 ◽  
Vol 27 (1) ◽  
pp. 74-82
Author(s):  
J. A. Seawright ◽  
M. Q. Benedict ◽  
S. Narang
Keyword(s):  
X Chromosome ◽  
Organizer Region ◽  
Nucleolar Organizer Region ◽  
Nucleolar Organizer ◽  
Chromosome Analysis ◽  
Anopheles Albimanus ◽  
Eye Color ◽  
Colour Mutant ◽  
Translocation Breakpoints ◽  
Radiation Induced

Snow (sn) is a recessive, eye color mutant that is phenotypically indistinguishable from the previously described mutant, white eye (we). The loci for these mutants are over 30 map units apart on the X chromosome. Analysis of salivary gland chromosomes of radiation-induced X-autosome translocations were used to define the positions of sn and we on the distal euchromatic portion of the long arm of the X chromosome. A recessive lethal trait (bubble head) was also mapped relative to we and sn, and the gene order on the long arm of the X chromosome is as follows: centromere – ? – snow – bubble head – white eye. Translocation breakpoints in the euchromatic portion of the X chromosome caused sterility or lethality in males hemizygous for the translocations, but breaks in the heterochromatin had no effect. Crossing-over was greatly reduced when translocation breakpoints were located in the euchromatic part of the X chromosome. The translocations were used to determine that the nucleolar organizer region is probably on the short arm of the X chromosome.Key words: Anopheles albimanus, eye colour mutant, X chromosome.

Chromosome studies in pelagic opisthobranch molluscs

1988 ◽  
Vol 66 (6) ◽  
pp. 1460-1473 ◽  
Author(s):  
Catherine Thiriot-Quiévreux
Keyword(s):  
Chromosome Number ◽  
Organizer Region ◽  
Nucleolar Organizer Region ◽  
Nucleolar Organizer ◽  
Diploid Chromosome Number ◽  
Evolutionary Trend ◽  
Submetacentric Chromosome ◽  
Opisthobranch Molluscs

Chromosome number and morphology were studied in nine species of pelagic opisthobranchs ("pteropods"). Among Thecosomata, seven species were investigated. Limacina inflata has a diploid chromosome number of 2n = 20 with metacentric and submetacentric chromosome pairs. Creseis acicula has 2n = 20 (five metacentric and five submetacentric pairs). Creseis virgula has 2n = 20 (seven metacentric, one submetacentric, one subtelocentric – submetacentric, and one submetacentric – subtelocentric pair). Clio pyramidata has 2n = 22 (five metacentric, one submetacentric, two submetacentric – subtelocentric, two subtelocentric, and one telocentric pair). Cavolinia inflexa has 2n = 24 (six metacentric, one submetacentric, two subtelocentric – submetacentric, one subtelocentric – telocentric, and two subtelocentric pairs). Peraclis reticulata has 2n = 24 (six metacentric and six submetacentric or subtelocentric pairs). Cymbulia peroni has 2n = 34 (six metacentric, three submetacentric, seven subtelocentric, and one telocentric pair). Among Gymnosomata, two species were investigated. Pneumodermopsis canephora has 2n = 32 (two metacentric, three submetacentric, four submetacentric – subtelocentric, one subtelocentric – submetacentric, five subtelocentric, and one telocentric – subtelocentric pair). Pneumoderma atlanticum has 2n = 32 (three metacentric, five submetacentric, four submetacentric – subtelocentric or subtelocentric – submetacentric, and four subtelocentric pairs). For three of the nine pteropod species, material was abundant enough to permit staining for the nucleolar organizer region. This region occurred on pair 9 in Creseis acicula, on pair 6 in Cavolinia inflexa and on pair 2 in Pneumodermopsis canephora. Results on number, morphology, and size of the chromosomes of each of the studied species are discussed. The present chromosomal evidence confirms the separation, sometimes seen as controversial, of the pelagic opisthobranchs into the orders Thecosomata and Gymnosomata. The Thecosomata constitute an isolated order among opisthobranchs by their striking chromosomal diversity. In contrast, the Gymnosomata show cytogenetic features that suggest an evolutionary trend with plesiomorphic characters, as in the Anaspidea and Sacoglossa.

A hybrid zone between Chorthippus parallelus parallelus and Chorthippus parallelus erythropus (Orthoptera: Acrididae): chromosomal differentiation

Genome ◽  
1988 ◽  
Vol 30 (5) ◽  
pp. 656-663 ◽  
Author(s):  
J. Gosálvez ◽  
C. López-Fernández ◽  
L. J. Bella ◽  
R. K. Butlin ◽  
G. M. Hewitt
Keyword(s):  
X Chromosome ◽  
Organizer Region ◽  
Nucleolar Organizer Region ◽  
Nucleolar Organizer ◽  
Hybrid Zones ◽  
Natural Conditions ◽  
Chorthippus Parallelus ◽  
Abnormal Sperm ◽  
Genetic Activity ◽  
Chromosomal Differentiation

Two subspecies of the meadow grasshopper Chorthippus parallelus form narrow hybrid zones in the Pyrenees. We studied the patterns of chromosome divergence to evaluate their possible role in the maintenance of such hybrid zones under natural conditions. The two subspecies share some common features such as identical chromosome number, similar basic chromosome form, and the GC-rich nature of all the heterochromatic DNA. Similar positions for the nucleolar organizer region (NOR) in two pairs of autosomes were also observed. The main difference was the presence of an active NOR in the X chromosome in Cp. parallelus that was absent from Cp. erythropus. The pattern of banding by C-banding, acridine orange, and chromomycin A3 also showed the subspecific characteristics on this chromosome. The presence or absence of an active NOR on the X chromosome was used to analyse the hybrid zones in two different transects of the Pyrenees, and clear clines of X NOR frequencies were observed passing from Cp. parallelus to Cp. erythropus. Some meiotic abnormalities were found in individuals from the hybrid zones with the subsequent production of abnormal sperm. Differences in genetic activity involving the sexual chromosome and the male sterility found in F1 hybrids produced in laboratory crosses are discussed as an example of Haldane's Rule.Key words: insect cytogenetics, hybrid zones, speciation.

scholarly journals Comparative FISH analysis of Senna tora tandem repeats revealed insights into the chromosome dynamics in Senna

2021 ◽  
Vol 43 (3) ◽  
pp. 237-249 ◽  
Author(s):  
Thanh Dat Ta ◽  
Nomar Espinosa Waminal ◽  
Thi Hong Nguyen ◽  
Remnyl Joyce Pellerin ◽  
Hyun Hee Kim
Keyword(s):  
Tandem Repeats ◽  
Chromosomal Rearrangements ◽  
Organizer Region ◽  
Nucleolar Organizer Region ◽  
Nucleolar Organizer ◽  
Pericentromeric Region ◽  
Its2 Sequence ◽  
Fish Analysis ◽  
Chromosomal Distribution ◽  
Chromosome Dynamics

Abstract Background DNA tandem repeats (TRs) are often abundant and occupy discrete regions in eukaryotic genomes. These TRs often cause or generate chromosomal rearrangements, which, in turn, drive chromosome evolution and speciation. Tracing the chromosomal distribution of TRs could therefore provide insights into the chromosome dynamics and speciation among closely related taxa. The basic chromosome number in the genus Senna is 2n = 28, but dysploid species like Senna tora have also been observed. Objective To understand the dynamics of these TRs and their impact on S. tora dysploidization. Methods We performed a comparative fluorescence in situ hybridization (FISH) analysis among nine closely related Senna species and compared the chromosomal distribution of these repeats from a cytotaxonomic perspective by using the ITS1-5.8S-ITS2 sequence to infer phylogenetic relationships. Results Of the nine S. tora TRs, two did not show any FISH signal whereas seven TRs showed similar and contrasting patterns to other Senna species. StoTR01_86, which was localized in the pericentromeric regions in all S. tora, but not at the nucleolar organizer region (NOR) site, was colocalized at the NOR site in all species except in S. siamea. StoTR02_7_tel was mostly localized at chromosome termini, but some species had an interstitial telomeric repeat in a few chromosomes. StoTR05_180 was distributed in the subtelomeric region in most species and was highly amplified in the pericentromeric region in some species. StoTR06_159 was either absent or colocalized in the NOR site in some species, and StoIGS_463, which was localized at the NOR site in S. tora, was either absent or localized at the subtelomeric or pericentromeric regions in other species. Conclusions These data suggest that TRs play important roles in S. tora dysploidy and suggest the involvement of 45S rDNA intergenic spacers in “carrying” repeats during genome reshuffling.

scholarly journals The genomic structure of a human chromosome 22 nucleolar organizer region determined by TAR cloning

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Jung-Hyun Kim ◽  
Vladimir N. Noskov ◽  
Aleksey Y. Ogurtsov ◽  
Ramaiah Nagaraja ◽  
Nikolai Petrov ◽  
...  
Keyword(s):  
Genomic Structure ◽  
Organizer Region ◽  
Nucleolar Organizer Region ◽  
Nucleolar Organizer ◽  
Chromosome 21 ◽  
Reference Sequence ◽  
Chromosome 22 ◽  
Rdna Variation ◽  
High Level ◽  
Tar Cloning

AbstractThe rDNA clusters and flanking sequences on human chromosomes 13, 14, 15, 21 and 22 represent large gaps in the current genomic assembly. The organization and the degree of divergence of the human rDNA units within an individual nucleolar organizer region (NOR) are only partially known. To address this lacuna, we previously applied transformation-associated recombination (TAR) cloning to isolate individual rDNA units from chromosome 21. That approach revealed an unexpectedly high level of heterogeneity in human rDNA, raising the possibility of corresponding variations in ribosome dynamics. We have now applied the same strategy to analyze an entire rDNA array end-to-end from a copy of chromosome 22. Sequencing of TAR isolates provided the entire NOR sequence, including proximal and distal junctions that may be involved in nucleolar function. Comparison of the newly sequenced rDNAs to reference sequence for chromosomes 22 and 21 revealed variants that are shared in human rDNA in individuals from different ethnic groups, many of them at high frequency. Analysis infers comparable intra- and inter-individual divergence of rDNA units on the same and different chromosomes, supporting the concerted evolution of rDNA units. The results provide a route to investigate further the role of rDNA variation in nucleolar formation and in the empirical associations of nucleoli with pathology.

Nucleolar organizer region staining patterns in paraffin-embedded tissue cells from human skin cancers

2005 ◽  
Vol 32 (5) ◽  
pp. 323-328 ◽  
Author(s):  
Rosana F. Romao-Correa ◽  
Durvanei A. Maria ◽  
Mithitaka Soma ◽  
Mirian N. Sotto ◽  
Jose Antonio Sanches ◽  
...  
Keyword(s):  
Human Skin ◽  
Organizer Region ◽  
Nucleolar Organizer Region ◽  
Nucleolar Organizer ◽  
Skin Cancers ◽  
Tissue Cells

Nucleologenesis in Trypanosoma cruzi

2016 ◽  
Vol 22 (3) ◽  
pp. 621-629 ◽  
Author(s):  
Tomás Nepomuceno-Mejía ◽  
Reyna Lara-Martínez ◽  
Roberto Hernández ◽  
María de Lourdes Segura-Valdez ◽  
Luis F. Jiménez-García
Keyword(s):  
Cell Division ◽  
Trypanosoma Cruzi ◽  
Ethylenediaminetetraacetic Acid ◽  
Organizer Region ◽  
Nucleolar Organizer Region ◽  
Light And Electron Microscopy ◽  
Nucleolar Organizer ◽  
Nuclear Bodies ◽  
Nucleolar Organizer Regions ◽  
Nucleolar Material

AbstractNucleolar assembly is a cellular event that requires the synthesis and processing of ribosomal RNA, in addition to the participation of pre-nucleolar bodies (PNBs) at the end of mitosis. In mammals and plants, nucleolar biogenesis has been described in detail, but in unicellular eukaryotes it is a poorly understood process. In this study, we used light and electron microscopy cytochemical techniques to investigate the distribution of nucleolar components in the pathway of nucleolus rebuilding during closed cell division in epimastigotes of Trypanosoma cruzi, the etiologic agent of American trypanosomiasis. Silver impregnation specific for nucleolar organizer regions and an ethylenediaminetetraacetic acid regressive procedure to preferentially stain ribonucleoprotein revealed the conservation and dispersion of nucleolar material throughout the nucleoplasm during cell division. Furthermore, at the end of mitosis, the argyrophilic proteins were concentrated in the nucleolar organizer region. Unexpectedly, accumulation of nucleolar material in the form of PNBs was not visualized. We suggest that formation of the nucleolus in epimastigotes of T. cruzi occurs by a process that does not require the concentration of nucleolar material within intermediate nuclear bodies such as mammalian and plant PNBs.

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