Figure 4.

The configuration of primary spermatocyte chromosomes in maturing oocytes (Method B). (a) Thirty minutes after electrofusion. The spermatocyte chromosomes have started to condense (arrow). The oocyte chromosomes are at prometaphase I (arrowheads). (b) One hour after electrofusion. The fully condensed spermatocyte chromosomes (arrows) are mingling with the oocyte chromosomes, which already have formed the Met I configuration (arrowheads, slightly out of focus). (c) Two hours after electrofusion. Both the spermatocyte and oocyte chromosomes are aligned on the Met I spindle of the oocyte, which has been arrested by cytochalasin treatment. Thus, the spermatocyte and oocyte chromosomes are successfully synchronized.