Chemical estimates of the RNA and DNA contents of the early mouse embryo

DNA and RNA were extracted from mouse embryos at several stages prior to implantation. RNA was measured by extinction at 200 nm, and DNA by a fluorometric assay. The mean values of RNA in the ovulated oocyte, 1‐cell, 2‐cell, and blastocyst‐stage embryo were 0.554, 0.545, 0.396, 0.458, and 1.37 ng, respectively. The mean values of DNA in embryos at these same stages were 23.8, 29.3, 41.1, 155, and 439 pg. There was no significant rise in total RNA per embryo until after the 8‐cell stage. The amount of DNA in mouse spermatozoa was also measured, and found to be 3.8 pg per spermato‐zoan. From this study it is clear that the mouse oocyte and early embryo do not contain the large quantities of DNA, in excess of the diploid value, found in some amphibian and invertebrate eggs.