SC abnormalities in pachytene spermatocytes: The same abnormalities were observed in all controls and patients, but with different frequencies: asynapsis, fragmented SC, dotted SC and thin SC (Fig.
The total percentage of nuclei with asynapsis varied from 0.65 to 5.98 per cent with a mean of 2.95 per cent for the controls (Table V), and 2.31 to 13.30 per cent with a mean of 7.97 per cent for the patients (Table VI).
Three of the meiotic abnormalities (asynapsis, SC fragmentation and irregular SC) have been described in electron microscopy earlier (24-28).
From the animal kingdom, evidence exists for the occurrence of different degrees of asynapsis among chromosome pairs in grasshoppers (Rees, 1957; John & Naylor, 1961), and Hewitt and John (1965) suggested some degree of autonomous control of each bivalent in grasshoppers.
In meiotic mutants asynapsis was restricted to the Aegilops chromosomes, whereas the Secale chromosomes paired normally.
speltoides (+ B's) the B-chromosomes were not found to have any effect on chiasma frequency, but in hybrids lacking the Ph gene the B-chromosomes were found to compensate for the missing gene, resulting in almost complete asynapsis (Dover & Riley, 1972, 1977; Vardi & Dover, 1972).