Deoxyribonucleic Acids of Sperm, Eggs and Somatic Cells of the Sea Urchin, Arbacia punctulata

Abstract

A SEARCH of the literature reveals no report of the comparative base composition of deoxyribonucleic acids isolated from the two gametes and the somatic cells of the same species. Yet the molecular events whereby genetic information from egg and sperm is integrated on fertilization are of fundamental importance in our understanding of the molecular basis of heredity and development in higher animals. These facts prompted the work recorded here, which is concerned with properties of the DNA isolated from sperm, eggs and adult somatic cells of the sea urchin Arbacia punctulata. Sperm and eggs were obtained either by the mild electric shock technique of Harvey¹ or by the injection of 0.5 M KCl² into the perivisceral cavity of adult sea urchins. The diploid tissues were obtained from spent adults, the gonads of which were discarded. The DNA from sperm and diploid tissues was isolated by a modification of the procedure described by Marmur³. High-molecular-weight DNA from eggs could not be prepared in this way unless the nuclei were first isolated by the method of Went and Mazia⁴. The hot phenol method⁵ was also effective in the isolation of DNA from whole eggs. Failure to isolate egg DNA by mild procedures might be due to the presence of potent deoxyribonucleases, which in turn could account for the inability of some investigators⁶ to obtain highly polymeric DNA from this source.