Equilocality of heterochromatin distribution and heterochromatin heterogeneity in acridid grasshoppers

Abstract

Comparative fluorescence studies on the chromosome of ten species of acridid grasshoppers, with varying amounts and locations of C-band positive heterochromatin, indicate that the only regions to fluoresce differentially are those that C-band. Within a given species there is a marked tendency for groups of chromosomes to accumulate heterochromatin with similar fluorescence behaviour at similar sites. This applies to all three major categories of heterochromatin - centric, interstitial and telomeric. Different sites within the same complement, however, tend to have different fluorescence properties. In particular, centric C-bands within a given species are regularly distinguishable in their behaviour from telomeric C-bands. Different species on the other hand, may show distinct forms of differential fluorescence at equilocal sites. These varying patterns of heterochromatin heterogeneity, both within and between species, indicate that whatever determines the differential response to fluorochromes has tended to operate both on an equilocal basis and in a concerted fashion. This is reinforced by the fact that structural rearrangements that lead to the relocation of centric C-bands, either within or between species, may also be accompanied by a change in fluorescence behaviour.

Autosomal, sex and B chromosomes in Eyprepocnemis plorans (Orthoptera) viewed with restriction endonuclease in situ digestion

“…Observations presented in this paper with the fluorochromes or those shown by John et al (1985), using the same dyes, also support this idea.…”

“…For instance, a positive homogeneous reaction to C-banding, usually identified as constitutive heterochromatin (Sumner, 1972), is now known not to represent the same type of material in a given organism (John et a!., 1985;Gosálvez et a!., 1987;LopezFernández eta!., 1989). In this study we used a number of techniques including in-Situ digestion with restriction endonucleases, to analyse the different types of chromatin present in the genome of the grasshopper Eyprepocnemis plorans.…”

Chromosomal markers in three species of the genus Mytilus (Mollusca: Bivalvia)

“…King (1980) and, later, other authors predicted that the differences in C-bands could be attributed to the addition or loss of heterochromatin; this process may be accompanied by chromosomal rearrangements such as fusions or fissions which would alter the morphology of the chromosome complement. Such types of changes have been described by Mayr et al (1985) in mammals and by John et a!. (1985) in grasshoppers.…”

Genome and chromosome disposition at somatic metaphase in a Hordeum × Psathyrostachys hybrid

“…A specific order of the chromosomes within the 203 genome of H vulgare, as reported by Bennett (1982Bennett ( , 1983Bennett ( , 1984a and Heslop-Harrison & Bennett (1983a,b, 1984, was not found by us (Linde-Laursen & Jensen, 1984). In addition, the validity of the finding and its theoretical and statistical bases have been questioned (Coates & Smith, 1984;Callow, 1985;John et al, 1985;Dorninger & Timischl, 1987;Rawlins & Shaw, 1988).…”