Chiasma distribution at diakinesis in the normal human male

Abstract

The chiasma distribution at diakinesis was investigated in one human male subject using cells triple-stained by the orcein, Q- and C-techniques. Evidence was obtained in favour of interference between chiasmata along the chromosome arms, even when the occurrence of one obligate chiasma per bivalent was taken into account. There was no indication of competition for chiasmata between different autosomes in the same cell. The chiasma distribution within chromosome arms was very similar to that observed in other organisms with no or only a moderate chiasma movement and no reduction in chiasma frequency during diplotene. The relevance of these findings for the estimation of the crossover frequency and for the interpretation of different models concerning the original location of chiasmata and their interrelation is discussed.