Intimate association between autosomal translocation trivalents and XY bivalents at pachytene was observed in a majority of cells of two men ascertained through primary sterility and found to be heterozygous for a 14;21 Robertsonian translocation. The association, studied by light and electron microscopy of spread first spermatocytes, was between the unpaired short arms of the normal chromosomes of the translocation trivalent and the differential axes of the XY chromosomes. In a minority of cells, this contact was not established, or not maintained, as alternative combinations between the elements available for non-homologous pairing were realized. Following a suggestion of Lifschytz and Lindsley (1972), sterility in these patients was attributed to spermatogenic arrest caused by physical contact of sex chromosomes with autosomal material and consequent interference with the normal metabolism of the sex chromosomes. Autosomal aberrations and polymorphisms, which lead to the presence of unpaired segments at meiosis, may thus play a critical role in a general mechanism of chromosomally-derived male sterility. It is proposed that such a mechanism may also be instrumental in the initiation of reproductive barriers in nature.

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The poorest visual acuity was found in those with OCA1A, which was associated with the highest rate of high hypermetropia (statistically significant different from other subgroups). Astigmatism was the most common visually significant refractive error across all subtypes of albinism. These results may help to clarify the prevalence of refractive errors in albino patients and aid the prediction of visual outcome in this heterogeneous population.

These results expand the genotype-phenotype correlation of ABCA4, showing that homozygosity for the novel c.4254-15del23 splicing mutation is associated with a severe progressive form of disease.