A Possible Influence of the Spindle Fibre on Crossing-Over in Drosophila

Abstract

The distribution of genes in the second and third chromosomes of Drosophila melanogaster suggests that crossing-over may be influenced by the spindle fibre at least in neighboring regions. The disparity between the genetic and cytological maps of these chromosomes especially in the spindle fibre regions (Dobzhanzky2'3) is consistent with such a view. Sturtevant4 suggests from studies of crossing-over in Drosophila stocks homozygous for inverted sections of the autosomes that crossing-over in a given region is a function of the material in that region rather than of its position in the chromosome. He found no significant changes in amount of crossing-over with change in position of a section of a chromosome with respect to the spindle fibre or the end of the chromosome. Muller and Stone5 in a study of crossing-over in the case of a homozygous inversion in the X-chromosome of Drosophila apparently found that the regions in the inverted section gave normal crossing-over. However, since in none of these cases of homozygous inversions did the inversion include regions close to the spindle fibre, the possibility remains that the spindle fibre influences crossing-over in regions close to it. Dobzhansky6 studied crossing-over in a homozygous III-IV translocation in Drosophila (designated as translocation-c) and found' no significant differences from normal controls. However, the regions which .might have been expected to be influenced by the spindle fibre were not studied. At the suggestion of Professor Dobzhansky, the Writer has made additional studies of crossing-over in flies homozygous for this translocation.-The results are reported in the present paper. In the translocation stock under consideration a distal segment made up of about three-fourths of the right limb of chromosome III (cytologically3) is broken off and attached to chromosome IV The break in chromosome III is close to and to the left of the curled gene (0.7 unit according to Dobzhanky's data3 and somewhat closer according to results obtained by the writer). Accordingly, in the homozygous translocation flies the section of the third chromosome including curled and regions to the right is closer to a spindle fibre (of the fourth chromosome) by a cytological distance equal to about one-fourth the length of the right limb of chromosome III. Genetically this distance represents about 2 crossover units (standard map7).

Physical mapping of restriction fragment length polymorphisms (RFLPs) in homoeologous group 7 chromosomes of wheat by in situ hybridization

“…This has also been seen in Drosophila where high levels of suppression of recombination are seen near the centromere (Roberts, 1965). This negative effect on crossing-over termed 'centromere effect' or 'spindle effect' by Beadle (1932) and Mather (1938) has also been demonstrated in yeast by Lambie & Roeder (1986) and in tomato by Ganal et a!. (1989).…”

Regulation of Recombination and Genomic Maintenance

“…In most organisms, such as humans, but not in the budding yeast Saccharomyces cerevisiae, centromeres are associated with large expanses of satellite repeat DNA (100 -250 Mbp in humans) that is packaged into constitutive heterochromatin (Talbert and Henikoff 2010). Centromeres were found to block crossovers, as noticed in the earliest genetic mapping studies (Sax 1930;Beadle 1932). Because HR between repeated DNA can lead to genomic rearrangements (George and Alani 2012), it was assumed that centromeres and heterochromatic repeat regions were devoid of HR, but recent discoveries provide intriguing new insights.…”

The role of repetitive DNA in structure and evolution of sex chromosomes in plants

“…Centromeres are regions with lower recombination frequency (Beadle, 1932;Clarke and Carbon, 1980) and often exhibit interspersion of satellite sequences and TEs, as in cereals (Zhong et al, 2002), Arabidopsis (Copenhaver et al, 1999), insects (Sun et al, 2003) and fungi (Cambareri et al, 1998). There are indications of the evolutionary link between the centromere structure and TE's activity: centromeric satellite repeats may arise from DNA transposons (Kapitonov and Jurka, 1999).…”