Somatic Association of Chromosomes in Barley

Abstract

Distances between pairs of homologous and nonhomologous telocentric chromosomes were measured in root tip cells of barley. The nonhomologous telocentrics were randomly distributed, whereas the homologues were significantly closer than would be expected with random distribution.

Distribution of human chromosomes on the metaphase plate. Symmetrical arrangement in human male cells

“…The chromosomes show an ordered arrangement on the metaphase plate that probably reflects their distribution in the nucleus. The symmetrical disposition of the homologues is compatible with their association in interphase (Feldman et al 1966;Egozcue, 1968;Fedak &Helgason, 1970 andYoshida, 1974), as the metaphase corresponds to a flattened nucleus. Their peculiar distribution in metaphase also confirms the absence of proximities between homologues described by Sele et al (1977).…”

“…(1) INTRODUCTION The distribution and relative positions of metaphase chromosomes have been extensively studied. According to most published results, the distribution of the chromosomes on the metaphase plate seems to be non-random, and may be related to the somatic association of the homologues (Feldman, Mello-Sampayo & Sears, 1966;Egozcue, 1968;Fedak &Helgason, 1970 andYoshida, 1974) or to some other type of ordered arrangement in interphase (Comings et al 1968). Probably the most important differences existing among the studies conducted so far depend on the statistical treatment of the data and on the effect of spindle poisons.…”

Mitotic spatial model: Arrangement of homologous chromosomes

“…Such observations were recently substantiated in several more critical cytological studies substituting the usual pretreatment chemicals with cold water for metaphase arrest, in order to minimise disruption and preserve, as much as possible, interphase chromosomal'distribution. Following cold treatment, somatic metaphase chromosomes were statistically analysed for their affinity distribution, in common wheat (Feldman et aL, 1972;Mello-Sampayo, 1973;Avivi et al, 1982), in Oats (Sadasivaiah et al, 1969;Thomas, 1973), in barley (Fedak & Helgason, 1970), in two wild species of Triticum (Kushnir, 1977), rye (Yoshida et aL, 1974) and in maize (Horn & Walden, 1978). Based on the analysis of distance values, it was clearly revealed in these studies that homologous partners lie closely associated.…”

The spatial order of chromosomes in root-tip metaphases ofAegilops umbellulata

“…(a) Somatic association of homologous chromosomes The present work used serially sectioned nuclei where accurate centromere positions in undisturbed nuclei were known and all chromosomes could be identified. Previously, studies have claimed to find degrees of somatic association of homologues, both in hexaploid wheat (see, for example , Feldman et al 1972;Mello-Sampayo 1973) and in other plants such as barley (Fedak & Helgason 1970) and Crepis (Lacadena et al 1977). These studies all used squashed preparations in the light microscope and often only a small number of chromosomes could be identified.…”