On the Heterogeneity of Heterochromatin

Rocchi, A.

doi:10.1080/00087114.1982.10796923

Cited by 15 publications

(8 citation statements)

References 61 publications

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“…Such a variety segment types which differ in their reactions to C-banding, demonstrate that, like the heterochromatin of the standard complement (Rocchi, 1982), supernumerary heterochromatin is also heterogeneous. Moreover this heterogeneity of extra heterochromatin needs to be taken into consideration before generalising the results obtained in investigations involving supernumerary chromosome segments.…”

Section: Discussior'mentioning

confidence: 99%

“…The heterochromatic nature of such supernumerary chromosome segments may be responsible for these effects. In view of the great heterogeneity of heterochromatin in the standard complement (Rocchi, 1982), it is of interest to discover whether the supernumerary heterochromatin is also heterogeneous and, if so, to search for a possible relation between the heterochromatic nature of each type of supernumerary segment and its effects on recombination. To date four types of extra segments have been detected in grasshoppers.…”

Section: Introductionmentioning

confidence: 99%

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C-Heterochromatin content of supernumerary chromosome segments of grasshoppers: Detection of an euchromatic extra segment

et al. 1984

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The response of 11 supernumerary segments to C-banding has been compared in six species of grasshoppers. A unique euchromatic supernumerary segment was present in the five populations of Omocestus bolivari analysed. It appears negatively heteropycnotic during the first prophase of meiosis and does not C-band. This euchromatic segment is distally located in the M6 chromosome and in every case was present in a heterozygous condition. It does not associate with the telomere of its unsegmented homologue and, consequently, the unequal M6 bivalents always segregate equationally for the extra segment in the first meiotic division. This euchromatic segment does not influence mean cell chiasma frequency but does influence chiasma position in the M6 bivalents carrying it. Four additional types of heterochromatic supernumerary chromosome segments may be distinguished in grasshoppers by C-banding: a) those darkly C-banded, b) those partly darkly C-banded, c) those lightly C-banded and d) those which do not C-band. All five types of segment appear to affect chiasma distribution in heterozygous monochiasmate bivalents but only those heterochromatic segments that do not C-band influence mean cell chiasma frequency.

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Section: Discussior'mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

C-Heterochromatin content of supernumerary chromosome segments of grasshoppers: Detection of an euchromatic extra segment

et al. 1984

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“…Meiosis involves four major n~chanisms (pairing, Both the heterochromatin of the standard compleexchange, orientation, and segregation), each of which ment (LaCour 1978;Rocchi 1982;John and King 1983; is under precise genetic control. Many gene mutants John et al 1985) and that appearing in a supernumerary affecting one or r1101-e of these n~chanisms have been condition (Camacho et al 1984) are heterogeneous in described in the literature (for a review see Baker et al, nature.…”

Section: Introductionmentioning

confidence: 99%

Specific chromosome breakage at meiosis in C-heterochromatin mutants of the grasshopper Euchorthippus pulvinatus

Santos¹,

Henriques‐Gil²,

Arana³

1985

Can. J. Genet. Cytol.

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Three males of Euchorthippus pulvinatus gallicus (Acrididae, Orthoptera) were found to be heterozygous for an enlarged interstitial C-block on the megameric chromosome, which usually has only small C-bands. These individuals exhibited a syndrome of chromosome breakages during the first meiotic division, the presence of the mutant C-bands being associated with the formation of specific weak points, as well as to an increase in sister chromatid cohesiveness. The pattern of breakage observed depends on the location of chiasmata relative to that of weak points and the enlarged C-block.Key words: C-heterochromatin mutant, chromosome breakage, weak point, sister chromatid cohesiveness.

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“…However, this feature is probably a necessary but not the only prerequisite for delayed condensation. There are other unknown factors relevant to chromosome condensation (Marcus et al, 1979;Rocchi, 1982;Felcher et al, 1982). The present work describes decondensation of Drosophila chromosomes in heterochromatic regions.…”

Section: Introductionmentioning

confidence: 99%

“…Therefore, chromosome regions with light satellite DNA are likely to be affected (i.e. H ÷ bands)Pimpinelli et al, 1976;Rocchi, 1982). The mean intensity of fluorescence of Drosophila interphase nuclei from neuroblasts after decondensation procedure.…”

mentioning

confidence: 99%

Specific decondensation of heterochromatic regions of Drosophila chromosomes-intrachromosomal and genomic control

et al. 1986

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The genomic and intrachromosomal control of condensation inhibition of heterochromatic regions of mitotic Drosophila chromosomes was studied. It is shown that decondensation is not a local property of the chromosomal regions. In particular the frequency and sometimes the pattern of decondensation is changed with translocations, inversions or loss of chromosomes. In a variety of deletions and inversions of X-chromosomal heterochromatin, which is usually decondensed, the phenomenon is absent or its pattern changed. A material effect is observed in interspecies hybrids between D. melanogaster and D. simulans: paternal chromosomes are neither more condensed or more decondensed under the influence of a maternal genome.

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On the Heterogeneity of Heterochromatin

Cited by 15 publications

References 61 publications

C-Heterochromatin content of supernumerary chromosome segments of grasshoppers: Detection of an euchromatic extra segment

C-Heterochromatin content of supernumerary chromosome segments of grasshoppers: Detection of an euchromatic extra segment

Specific chromosome breakage at meiosis in C-heterochromatin mutants of the grasshopper Euchorthippus pulvinatus

Specific decondensation of heterochromatic regions of Drosophila chromosomes-intrachromosomal and genomic control

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