[quote=MDinanaI think you're correct. Faster growing/reproducing organ systems get hit first. Marrow, GI tract and testes tend to reproduce fastest (ovaries probably aren't, since eggs are present at birth). Hence chemo drugs tend to affect these places first, as well. [/quote]

Since radiation damage is cumulative, allowing persons of child-bearing age equipped with ovaries to work in radiation areas isn't a good idea from a birth defects risk point of view.

Testes, while containing fast-growing cells which have a chance of propagating a radiation-induced defect, have their fast-growing cells changed out rather than carrying the vulnerable cells for decades. Hence allowing persons equipped with testes would be the better choice from a birth defects point of view.