The purpose of this thesis was to obtain new data about the development of the mouse embryo during preimplantation stages. The research was based on Dr. Clare Chatot's earlier experiments and data which indicated that glutamine is used as an energy substrate in preimplantation mouse embryos and that the enzyme glutaminase was present in all preimplantation stages. We hypothesized that the next step in the embryo's metabolism would be the utilization of the enzyme glutamate dehydrogenase to convert glutamate to aketoglutarate. The experimental purpose was to detect this enzyme at the 1-cell, 2-cell, 8-cell and blastocyst stages of the embryo's development. The paper provides background information obtained from previous experiments, which helped develop our hypothesis. Experiments were completed to test the hypothesis. Results provided control data suggesting that the PCR reaction and RNA preparation were working efficiently. Finally, the paper discusses the results and the conclusions drawn from them.