Meiotic behaviour of familial pericentric inversions of chromosomes 1 and 9.

Pachytene analysis was carried out in two infertile brothers, one heterozygous for two pericentric inversions of chromosomes 1 and 9, the second heterozygous for the pericentric inversion of chromosome 1. The synaptic behaviour of the bivalent 1 inversion was the most informative. Analysis of the chromomere pattern combined with centromeric heterochromatin staining and synaptonemal complexes visualization allowed precise description of synaptic initiation and extension leading to the homosynapsed loop. Heterosynapsis following alignment of the inverted segments was demonstrated. Non-homologous synapsed bivalents had the morphological aspects of straight bivalents with two distant blocks of centromeric heterochromatin. The possible sterilizing effect caused by the autosomal inversion is discussed.