ULTRAVIOLET LIGHT AND THE MITOTIC CYCLE IN THE SEA URCHIN'S EGG

Abstract

The effect of u.v. radiation in delaying certain events in the cell division cycle of Arbacia punctulata was examined. The period before fusion of the erg and sperm nucleus is unaffected by doses of u.v. that cause considerable delay in other parts of the cycle. The principal delay occurs before anaphase. Between anaphase and cleavage delay is only slight The "refractory period"" during which radiation fails to delay the immediate cycle of cell division, apparently does not represent complete refractoriness of the mitotic cycle to interference during this period.