The effect of apholate and thiotepa on nucleic acid synthesis and nucleotide ratios in housefly eggs

The nucleic acid synthesis in normal viable housefly eggs and non-viable housefly eggs deposited by flies chemosterilized by apholate and thiotepa has been studied. During normal embryonic development, there is a rapid many-fold increase in DNA after an initial lag period. In the chemosterilized eggs there is almost no increase in DNA, but some accumulation of the deoxyribosidic components of the acid-soluble extract. The effect on the levels of RNA and ribosidic components of the acid-soluble extract is less apparent.The nucleotide ratios of normal housefly eggs has been determined to be similar to that reported for other insect eggs. Apholate-sterilized eggs were significantly lower in adenylic acid than normal fly-egg RNA. The RNA of the thiotepa sterilized eggs was a little lower in guanylic acid and contained an unidentified compound not present in normal egg RNA.When thiotepa P³² was the chemosterilant, all components of the isolated sodium RNA were labelled. This suggests that thiotepa may have been degraded and the resulting inorganic phosphate reincorporated into the RNA. There was no evidence of alkylated guanine in the RNA.