Presynaptic association of homologous chromosomes is a prerequisite to the sequence of events that lead to chiasma formation. This association of homologous chromosomes, as entire units, occurs with probability a, and chiasma formation occurs independently in opposite chromosome arms with probability c. a and c have been estimated from frequencies of different chromosome configurations at metap...

The segregation of chromosomes 13 distinguishable by Q band fluorescent polymorphisms has been studied in three families with retinoblastoma. The recombination fraction for two of these families and four families previously reported did not differ significantly from 50%. Since a high recombination fraction has been predicted from chiasma frequency between the centromere of chromosome 13 and 13q...

Thirty patients with chiasma syndrome attributed to ischemic processes of various origins are described. The initial diagnosis was made after an investigation based on polytome pneumoencephalography and angiography. This diagnosis was confirmed later with the use of high-resolution computed tomography (CT) and refined angiographic techniques. The ischemic chiasma syndrome may be classified into...