AN ANALYSIS OF T H E INACTIVATION OF THE FROG SPERM NUCLEUS BY TOLUIDINE BLUE* By ROBERT BRIGGS

Many years ago Hertwig (1) and Dalcq (2) showed that trypaflavine has the property of inactivating the frog sperm nucleus without affecting the extranuclear parts of the cell. Following an appropriate treatment with the dye, the sperm cells still retain their capacity to activate eggs, but contribute no chromosomes to the resulting embryos, which then develop as haploids with the maternal chromosomes only. These early investigations were concerned mainly with the use of the dye as a tool in studying the role of the nucleus in embryonic development. The nature of the reaction between the dye and the sperm nucleus was not itself analyzed at that time and, so far as we know, has not since received any serious attention. Yet, as we shall t ry to show later on, this reaction presents an unusual opportunity for a quantitative study of chromosome chemistry in relation to chromosome function. Since the time of Hertwig's and Dalcq's investigations considerable chemical work has been done on the reactions between basic dyes and nucleic acids. Therefore, in the present study it was desirable at the outset to test several dyes in order to see whether any of them offer advantages over trypaflavine as specific inactivators of the sperm nucleus. The dyes tested were toluidine blue, methylene blue, thionine, acriflavine (trypaflavine), pyronin, methyl green, and crystal violet. All except the triphenylmethanes (methyl green and crystal violet) were found to inactivate the sperm nucleus without damaging appreciably the extranuclear parts. The thiazin dyes were particularly effective. For example, an appropriate treatment with toluidine blue inactivated the sperm nucleus completely, leaving the sperm otherwise unaffected, so that eggs inseminated with the treated sperm developed uniformly as typical gynogenetic haploids. Other dyes mentioned above as being effective could produce the same result, but none offered advantages over toluidine blue and it was therefore selected for the experiments reported here.