Nucleoprotein methylation in salivary gland chromosomes of Sciara coprophila: Correlation with DNA synthesis

Methylation and ethylation of chromosomal nucleoproteins have been demonstrated in the salivary glands of Sciara coprophila larvae. A difference in grain distribution pattern was observed between chromosomes incubated in ³H-methyl-methionine and ³H-ethyl-ethionine. Like DNA synthesis, methylation could only be demonstrated at certain developmental stages, and during some of these a close correlation was observed between labelling patterns following ³H-methyl-methionine and ³H-thymidine in separated gland pairs. No such correlation was observed with RNA synthesis. Ethylation of chromosomal non-histone protein could not be correlated with nucleic acid biosynthesis. Feeding ethionine during larval development produced similar nucleolar abnormalities to those previously described in rat liver nucleoli.