Karyotypic Evolution in Gehyra (Gekkonidae: Reptilia) III.* The Gehyra australis Complex

1983 ◽  
Vol 31 (5) ◽  
pp. 723 ◽  
Author(s):  
M King
Keyword(s):  
Chromosome Morphology ◽  
Chromosome Rearrangements ◽  
Karyotypic Evolution ◽  
Karyotypic Analysis ◽  
Chromosome Races ◽  
The Relationship ◽  
Gehyra Variegata

A karyotypic analysis of the widely distributed Australian gekko Gehyra australis has revealed a complex of chromosome races. Each of these is fixed for a particular karyomorph, and is found over a geographically delimited distribution. The seven chromosome races differ by number, or chromosome morphology, and are defined as: 2n=44,2n=42a, 2n=42b, 2n=42c, 2n=40a, 2n=40b, 2n=38. In addition, a series of animals from these races possess novel chromosome rearrangements. A model for the evolution of this complex of races is proposed, and the relationship ofthese forms to each other and to members of the Gehyra variegata-punctata complex is discussed.

Karyotypic Evolution in Gehyra (Gekkonidae: Reptilia) I. The Gehyra Variegata-Punctata Complex.

1979 ◽  
Vol 27 (3) ◽  
pp. 373 ◽  
Author(s):  
M King
Keyword(s):  
Phylogenetic Relationships ◽  
Karyotypic Evolution ◽  
Isolated Populations ◽  
Karyotypic Analysis ◽  
Geographic Barriers ◽  
Chromosome Races ◽  
Chromosome Fusions ◽  
Morphological Differences ◽  
Gehyra Variegata

A karyotypic analysis of populations of the gekkos Gehyra variegata and G. punctata reveals three chromosome races in G. variegata (2n = 44; 2n = 40a; 2n = 40b), and three in G. punctata (2n = 44; 2n = 42; 2n = 38). The chromosome races have differentiated by a series of chromosome fusions. The ordered nature of these changes suggests that the phylogenetic relationships of the races cut across the current taxonomy, and it is argued that there is but one 2n = 44 race, occurring as a number of morphologically distinct populations, two of which were erroneously described as the separate Gehyra species. Isolated populations within a number of the chromosome races show pronounced morphological differences. It is believed that these gekkos are an ancient Australian group which differentiated chromosomally during a number of colonizing radiations. Since then, populations within each race have been isolated by geographic barriers and have speciated allopatrically. This suggests that the chromosome races are at least good species and may be of a higher taxon.

scholarly journals Nucleic acid content and Chromosome morphology in Chrysanthemum

1969 ◽  
Vol 13 (3) ◽  
pp. 241-250 ◽  
Author(s):  
G. J. Dowrick ◽  
A. S. El Bayoumi
Keyword(s):  
Nucleic Acid ◽  
Chromosome Number ◽  
Dna Content ◽  
Chromosome Numbers ◽  
Chromosome Length ◽  
Chromosome Morphology ◽  
Nucleic Acid Content ◽  
Chromosome Size ◽  
Dna Contents ◽  
The Relationship

1. The DNA contents of twenty-eight different species and forms of Chrysanthemum have been measured by photometry. It is shown that there are large differences in DNA content between some species with identical chromosome numbers.2. The DNA contents of natural polyploids are frequently not those expected when comparison is made with diploid forms of the same species. The DNA contents of induced polyploids are those expected.3. Chromosome length and volume are positively correlated with DNA content.4. The relationship between chromosome number, chromosome size, DNA content and gene number is considered, and it is suggested that the differences in DNA content may result from the presence of differing amounts of genetically inactive DNA in the chromosomes.

Variable conservation of nucleolus organizer regions during karyotypic evolution in Microtidae

Genome ◽  
1990 ◽  
Vol 33 (1) ◽  
pp. 119-122 ◽  
Author(s):  
A. Sánchez ◽  
M. Burgos ◽  
R. Jiménez ◽  
R. Díaz de la Guardia
Keyword(s):  
Comparative Study ◽  
Nucleolus Organizer ◽  
Chromosome Rearrangements ◽  
Karyotypic Evolution ◽  
Nucleolus Organizer Regions ◽  
The Comparative Study

The location of the nucleolus organizer regions (NORs) was studied in four species of Microtidae (Microtus nivalis, M. cabrerae, M. arvalis, and Arvicola sapidus). The comparative study of these locations shows that some NORs have been conserved despite the chromosome rearrangements that have occurred through karyotypic evolution, while others have been lost. In addition, there are many chromosomes in which NORs seem to have appeared or been lost without apparent relation to the chromosome rearrangements. Some hypotheses regarding these facts are discussed in the text.Key words: nucleolus organizer regions, Microtidae, karyotypic evolution.

scholarly journals Molecular Composition of Heterochromatin and Its Contribution to Chromosome Variation in the Microtus thomasi/Microtus atticus Species Complex

Genes ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 807
Author(s):  
Michail Rovatsos ◽  
Juan Alberto Marchal ◽  
Eva Giagia-Athanasopoulou ◽  
Antonio Sánchez
Keyword(s):  
Repetitive Dna ◽  
Species Complex ◽  
Sex Chromosome ◽  
Chromosomal Rearrangements ◽  
Chromosome Morphology ◽  
Dna Motifs ◽  
Telomeric Sequences ◽  
Chromosome Races ◽  
Chromosomal Races ◽  
Dna Elements

The voles of the Microtus thomasi/M. atticus species complex demonstrate a remarkable variability in diploid chromosomal number (2n = 38–44 chromosomes) and sex chromosome morphology. In the current study, we examined by in situ hybridization the topology of four satellite DNA motifs (Msat-160, Mth-Alu900, Mth-Alu2.2, TTAGGG telomeric sequences) and two transposons (LINE, SINE) on the karyotypes of nine chromosome races (i.e., populations with unique cytogenetic traits) of Microtus thomasi, and two chromosomal races of M. atticus. According to the topology of the repetitive DNA motifs, we were able to identify six types of biarmed chromosomes formed from either Robertsonian or/and tandem fusions. In addition, we identified 14 X chromosome variants and 12 Y chromosome variants, and we were able to reconstruct their evolutionary relations, caused mainly by distinct mechanisms of amplification of repetitive DNA elements, including the telomeric sequences. Our study used the model of the Microtus thomasi/M. atticus species complex to explore how repetitive centromeric content can alter from chromosomal rearrangements and can shape the morphology of sex chromosomes, resulting in extensive inter-species cytogenetic variability.

Karyotypes and meiosis of the Australian Tettigoniidae (Orthoptera) II. The genus Nanodectes Rentz (Tettigoniinae)*

1991 ◽  
Vol 5 (1) ◽  
pp. 33 ◽  
Author(s):  
N Ueshuma ◽  
DCF Rentz
Keyword(s):  
Chromosome Number ◽  
X Chromosome ◽  
Chromosome Evolution ◽  
Centric Fusion ◽  
Chromosome Rearrangements ◽  
Karyotypic Evolution ◽  
Telocentric Chromosome ◽  
Species Ranges ◽  
Tandem Fusion ◽  
Different Populations

The karyotypes and meioses from males of the species in the shield-backed katydid genus Nanodectes Rentz (Tettigoniinae) have been studied. The chromosome number of these species ranges from 2n = 15 to 2n =23 in the male. The male karyotypes were all X – 0 and the X was always the largest telocentric chromosome. Four types of chromosome systems are found in different populations of N. triodiae Rentz: 2n = 15 (6 metacentric + 8 telocentric autosomes + X), 2n = 15 (4 metacentric + 10 telocentric autosomes + X), 2n = 17 (4 metacentric+ 12 telocentric autosomes + X) and 2n = 19 (2 metacentric + 16 telocentric autosomes + X). Chromosome rearrangements, such as centric fusion and tandem fusion, appear to have played an important role in chromosome evolution at the inter- and intra-specific levels in Nanodectes. Possible pathways of karyotypic evolution and speciation are discussed.* Part I: pp. 303-51 in: 'The Tettigoniidae: Biology, Ecology, Systematics'. Eds W. J. Bailey and D. C. F. Rentz. (Crawford House: Bathurst.)

scholarly journals Vertebrate Chromosome Evolution

2020 ◽  
Vol 9 (1) ◽  
Author(s):  
Joana Damas ◽  
Marco Corbo ◽  
Harris A. Lewin
Keyword(s):  
Chromosome Evolution ◽  
De Novo ◽  
Detailed Examination ◽  
Chromosome Rearrangements ◽  
Annual Review ◽  
Publication Date ◽  
Phenotypic Evolution ◽  
Sequencing Technology ◽  
Genome Assemblies ◽  
The Relationship

The study of chromosome evolution is undergoing a resurgence of interest owing to advances in DNA sequencing technology that facilitate the production of chromosome-scale whole-genome assemblies de novo. This review focuses on the history, methods, discoveries, and current challenges facing the field, with an emphasis on vertebrate genomes. A detailed examination of the literature on the biology of chromosome rearrangements is presented, specifically the relationship between chromosome rearrangements and phenotypic evolution, adaptation, and speciation. A critical review of the methods for identifying, characterizing, and visualizing chromosome rearrangements and computationally reconstructing ancestral karyotypes is presented. We conclude by looking to the future, identifying the enormous technical and scientific challenges presented by the accumulation of hundreds and eventually thousands of chromosome-scale assemblies. Expected final online publication date for the Annual Review of Animal Biosciences, Volume 9 is February 16, 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Interstellar gas in the central region of the Galaxy

1967 ◽  
Vol 31 ◽  
pp. 239-251 ◽  
Author(s):  
F. J. Kerr
Keyword(s):  
Central Region ◽  
Galactic Plane ◽  
Neutral Hydrogen ◽  
Continuum Emission ◽  
Galactic Centre ◽  
Interstellar Gas ◽  
Hydrogen Recombination ◽  
The Galaxy ◽  
Centre Region ◽  
The Relationship

A review is given of information on the galactic-centre region obtained from recent observations of the 21-cm line from neutral hydrogen, the 18-cm group of OH lines, a hydrogen recombination line at 6 cm wavelength, and the continuum emission from ionized hydrogen.Both inward and outward motions are important in this region, in addition to rotation. Several types of observation indicate the presence of material in features inclined to the galactic plane. The relationship between the H and OH concentrations is not yet clear, but a rough picture of the central region can be proposed.

The relationship of the scleractinian corals to the rugose corals

Paleobiology ◽  
1980 ◽  
Vol 6 (02) ◽  
pp. 146-160 ◽  
Author(s):  
William A. Oliver
Keyword(s):  
Critical Points ◽  
Scleractinian Corals ◽  
Convincing Evidence ◽  
Early Triassic ◽  
Rugose Corals ◽  
History Of ◽  
The Subject ◽  
Relationship Of ◽  
The Relationship ◽  
Biologic Factors

The Mesozoic-Cenozoic coral Order Scleractinia has been suggested to have originated or evolved (1) by direct descent from the Paleozoic Order Rugosa or (2) by the development of a skeleton in members of one of the anemone groups that probably have existed throughout Phanerozoic time. In spite of much work on the subject, advocates of the direct descent hypothesis have failed to find convincing evidence of this relationship. Critical points are:(1) Rugosan septal insertion is serial; Scleractinian insertion is cyclic; no intermediate stages have been demonstrated. Apparent intermediates are Scleractinia having bilateral cyclic insertion or teratological Rugosa.(2) There is convincing evidence that the skeletons of many Rugosa were calcitic and none are known to be or to have been aragonitic. In contrast, the skeletons of all living Scleractinia are aragonitic and there is evidence that fossil Scleractinia were aragonitic also. The mineralogic difference is almost certainly due to intrinsic biologic factors.(3) No early Triassic corals of either group are known. This fact is not compelling (by itself) but is important in connection with points 1 and 2, because, given direct descent, both changes took place during this only stage in the history of the two groups in which there are no known corals.

Choosing a Markov blanket

2020 ◽  
Vol 43 ◽  
Author(s):  
Thomas Parr
Keyword(s):  
Markov Blanket ◽  
Target Article ◽  
The Relationship

Abstract This commentary focuses upon the relationship between two themes in the target article: the ways in which a Markov blanket may be defined and the role of precision and salience in mediating the interactions between what is internal and external to a system. These each rest upon the different perspectives we might take while “choosing” a Markov blanket.

Tinkering with cognitive gadgets: Cultural evolutionary psychology meets active inference

2019 ◽  
Vol 42 ◽  
Author(s):  
Paul Benjamin Badcock ◽  
Axel Constant ◽  
Maxwell James Désormeau Ramstead
Keyword(s):  
Evolutionary Psychology ◽  
Research Program ◽  
Active Inference ◽  
Innovative Research ◽  
Cognitive Faculties ◽  
Cultural Evolutionary ◽  
The Relationship

Abstract Cognitive Gadgets offers a new, convincing perspective on the origins of our distinctive cognitive faculties, coupled with a clear, innovative research program. Although we broadly endorse Heyes’ ideas, we raise some concerns about her characterisation of evolutionary psychology and the relationship between biology and culture, before discussing the potential fruits of examining cognitive gadgets through the lens of active inference.

Sign in / Sign up

Export Citation Format

Share Document