Reversing chromatin accessibility differences that distinguish homologous mitotic metaphase chromosomes

Cytological descriptions are given for two sympatric sibling species, Simulium praelargum IIIL-st and Simulium praelargum IIIL-1.2, from Darjeeling, West Bengal, India. Sibling IIIL-1.2 differs from IIIL-st by a two step fixed included inversion (IIIL-1.2) found on the long arm of chromosome III. Both siblings possess heterochromatinized IIIS polytene chromosome ends, while IIIL-1.2 is unique within the Simuliidae in that it exhibits a very large enhanced chromocentre that persists in normal somatic tissue, contrary to other chromocentre-containing taxa. In IIIL-1.2, the chromocentre occurs as a positively allocyclic heteropycnotic body in normal mitotic interphase cells of neuroblast ganglia, oogonia, and spermatogonia. In mitotic metaphase chromosomes, the chromocentre forms large pronounced primary (centromere) constrictions and appears to be associated with nonhomologous pairing. Initial cytological studies on taxa within the feuerborni group have revealed heterochromatic chromosomal polymorphisms. Progressive fixation of these polymorphisms in different taxa within the group opens up the possibility of using comparative molecular or genomic approaches to begin to define the functional and structural aspects of the epigenome and to further characterize mitosis and meiosis in S. praelargum IIIL-1.2.

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Heterochromatin, the synaptonemal complex and crossing over

Journal of Cell Science ◽

10.1242/jcs.71.1.159 ◽

1984 ◽

Vol 71 (1) ◽

pp. 159-176 ◽

Cited By ~ 1

Author(s):

S.M. Stack

Keyword(s):

Electron Microscopy ◽

Lycopersicon Esculentum ◽

Synaptonemal Complex ◽

Electron Microscopic Examination ◽

Differential Staining ◽

Crossing Over ◽

Mitotic Metaphase ◽

Plantago Ovata ◽

Electron Microscopic ◽

Metaphase Chromosomes

A combined light- and electron-microscopic examination of chromosomes from two angiospermous plants, Plantago ovata and Lycopersicon esculentum, and a mammal, Mus musculus, was performed. From this investigation three observations have been made that may be relevant to the observed lack of crossing over in heterochromatin. (1) Differential staining indicates that heterochromatin represents a smaller fraction of the length of pachytene chromosomes than it represents in the length of mitotic metaphase chromosomes. Since the synaptonemal complex (SC) runs throughout the length of these pachytene chromosomes, it is under-represented in heterochromatin. Considering the evidence for a rough correlation between the length of SC and the amount of crossing over, this could result in less crossing over in heterochromatin than expected on the basis of its length in mitotic metaphase chromosomes. (2) Electron microscopy indicates that, unlike the SC in euchromatin, the SC in heterochromatin is densely ensheathed in highly compact chromatin. If crossing over occurs in the SC or even in the surrounding chromatin, the compaction of the chromatin may prevent the penetration of enzymes needed in recombination. (3) Finally, a difference in the structure of SCs in euchromatin versus heterochromatin was observed that could be associated with the lack of crossing over in heterochromatin.

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Metaphase karyotype identity in four homosequential Drosophila species from Hawaii

Canadian Journal of Genetics and Cytology ◽

10.1139/g85-045 ◽

1985 ◽

Vol 27 (3) ◽

pp. 308-311 ◽

Cited By ~ 3

Author(s):

Linda S. Chang ◽

Hampton L. Carson

Keyword(s):

Polytene Chromosome ◽

Chromosomal Rearrangements ◽

The Other ◽

Drosophila Species ◽

Mitotic Metaphase ◽

Metaphase Chromosomes ◽

Hawaiian Drosophila ◽

Gross Chromosomal Rearrangements ◽

Rule Out

Four recently evolved species of Hawaiian Drosophila (silvestris, heteroneura, dijferens, and planitibia) have previously been shown to be homosequential in all five polytene chromosome arms. This suggests that the changes involved in speciation are at the genic level and hence are not evident in the polytene banding sequences. Because this does not rule out the occurrence of heterochromatic differences between these homosequential species, the present study was carried out to examine this possibility. These species are now shown to have identical heterochromatin distributions in mitotic metaphase chromosomes. This proves that neither gross chromosomal rearrangements nor novel heterochromatic blocks have been involved in the divergence of these four species. A fifth, and evolutionarily more distant, species (hemipeza) belonging to the same subgroup has a significantly different heterochromatin distribution from the other four species.Key words: heterochromatin, metaphase karyotypes, Hawaiian Drosophila.

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Cluster analysis of karyotype similarity coefficients in Epimedium (Berberidaceae): insights in the systematics and evolution

PhytoKeys ◽

10.3897/phytokeys.161.51046 ◽

2020 ◽

Vol 161 ◽

pp. 11-26

Author(s):

Lin-Jiao Wang ◽

Meng-Di Gao ◽

Mao-Yin Sheng ◽

Jie Yin

Keyword(s):

Genetic Diversity ◽

Cluster Analysis ◽

Geographical Distribution ◽

Karyotype Analysis ◽

Resource Utilisation ◽

Mitotic Metaphase ◽

Interspecific Relationship ◽

Similarity Coefficients ◽

Metaphase Chromosomes ◽

Homologous Chromosomes

In order to evaluate the genome evolution and systematics, karyotype analysis of mitotic metaphase chromosomes in 51 taxa of Epimedium and two species of Vancouveria was conducted. The 53 taxa were clustered, based on their karyotype similarity coefficients. Results showed that the 53 taxa studied were all diploid with 12 chromosomes (2n = 2x = 12). Each taxon had one pair of satellites located on pair I of homologous chromosomes. Moreover, the karyotype types of the 53 taxa studied were all type 1A or 2A of Stebbins. It can be concluded that the karyotypes between species are indeed very similar and the genome of Epimedium was conservative in evolution. The cluster analysis of karyotype similarity coefficients could provide valuable clues for the systematics and taxonomy of Epimedium. Results of the cluster analysis strongly supported the previous taxonomic division of E. subg. Rhizophyllum and E. subg. Epimedium. The results also showed that the interspecific relationship was closely correlated with geographical distribution in E. subg. Epimedium and the taxa native to east Asia had the highest genetic diversity in Epimedium. Finally, the origin of the modern geographical distribution of Epimedium was inferred. Results of the present study have significant scientific values in further studies on resource utilisation, taxonomy and phylogeny in Epimedium.

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Chromosomes of the tsetse fly, Glossina palpalis R.-D.

Parasitology ◽

10.1017/s0031182000069614 ◽

1968 ◽

Vol 58 (4) ◽

pp. 835-838 ◽

Cited By ~ 7

Author(s):

K. Riordan

Keyword(s):

Nervous Tissue ◽

Diploid Number ◽

Tsetse Fly ◽

Mitotic Metaphase ◽

Metaphase Chromosomes ◽

Glossina Palpalis

Mitotic metaphase chromosomes of the tsetse fly Glossina palpalis R.-D. have been investigated.The chromosomes studied were in circumoesophageal nervous tissue from young pupae, stained with aceto-orcein and spread by squashing.The diploid number of chromosomes was shown to be 6, consisting of 2 long pairs and 1 short pair at metaphase.This finding is discussed briefly in relation to previous descriptions of the chromosomes of G. tachinoides West. and G. morsitans morsitans West. and to accepted systematic divisions of the genus Glossina into subgeneric groups.I wish to thank Mr H. Dickson for assistance with photography. I thank Mr D. A. T. Baldry for advice and suggestions concerning the manuscript. Mr T. M. Leach has also made suggestions concerning the manuscript, and as Director of the Nigerian Institute for Trypanosomiasis Research, has given his permission to publish this paper.

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Localized, non-random differences in chromatin accessibility between homologous metaphase chromosomes

Molecular Cytogenetics ◽

10.1186/s13039-014-0070-y ◽

2014 ◽

Vol 7 (1) ◽

Cited By ~ 5

Author(s):

Wahab A Khan ◽

Peter K Rogan ◽

Joan HM Knoll

Keyword(s):

Chromatin Accessibility ◽

Metaphase Chromosomes

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Kinetochore microtubule numbers of different sized chromosomes

The Journal of Cell Biology ◽

10.1083/jcb.83.3.556 ◽

1979 ◽

Vol 83 (3) ◽

pp. 556-561 ◽

Cited By ~ 24

Author(s):

PB Moens

Keyword(s):

Evolutionary History ◽

Spindle Pole ◽

Mitotic Metaphase ◽

Robertsonian Fusion ◽

Metaphase Chromosomes ◽

History Of ◽

The Individual ◽

Kinetochore Region ◽

Mitosis And Meiosis ◽

Metaphase I

For three species of grasshoppers the volumes of the largest and the smallest metaphase chromosome differ by a factor of 10, but the microtubules (MTs) attached to the individual kinetochores show no corresponding range in numbers. Locusta mitotic metaphase chromosomes range from 2 to 21 μm, and the average number of MTs per kinetochore is 21 with an SD of 4.6. Locusta meiotic bivalents at late metaphase I range from 4 to 40 μm(3), and the kinetochore regions (= two sister kinetochores facing the same spindle pole) have an average of 25 kinetochore microtubules (kMTs) with an SD of 4.9. Anaphase velocities are the same at mitosis and meiosis I. The smaller mitotic metaphase chromosomes of neopodismopsis are similar in size, 6 to 45 μm(3), to Locusta, but they have an average more kMTs, 33, SD = 9.2. The four large Robertsonian fusion chromosomes of neopodismopsis have an average of 67 MTs per kinetochore, the large number possibly the result of a permanent dicentric condition. Chloealtis has three pairs of Robertsonian fusion chromosomes which, at late meiotic metaphase I, form bivalents of 116, 134, and 152 μm (3) with an average of 67 MTs per kinetochore similar to Locusta bivalents, but with a much higher average of 42 MTs per kinetochore region. It is speculated that, in addition to mechanical demands of force, load, and viscosity, the kMT numbers are governed by cell type and evolutionary history of the karyotype in these grasshoppers.

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