Three cases of low chiasma frequency associated with infertility in man.

Three new cases of low chiasma frequency in infertile men are described. In the first case, all cells showed abnormal diakineses; in the second, 20% of the diakineses were desynaptic, while the remaining 80% were normal; in the third, all diakineses were desynaptic and showed chromosome fragmentation. The possible mechanisms leading to asynapsis, desynapsis or precocious chiasma terminalization are discussed.