Abstract
A method for estimating the methylation of uridine-monophosphate (UMP) and d-UMP in tissue extracts is presented. By this procedure it has been demonstrated that UMP is converted to 5-methyl UMP in extracts of rat embryos. This reaction requires the presence of tetrahydro-folic acid and formaldehyde and appears to be a accompanied by intermediates or side products, as revealed by radioautography.