- MCM (minichromosome maintenance) gene family of Saccharomyces cerevisiae encodes essential DNA replication factors that participate in the initiation of DNA replication. In addition, their localization to the nucleus in a mitosis-dependent manner fueled the hypothesis that MCMs also act to couple DNA replication to mitosis. We report the identification of a Drosophila gene family with extensive sequence identity to the MCM genes. Results from antibody injection experiments suggest that MCMs play an essential role in DNA replication during embryogenesis. Evolutionary conservation of MCM sequences and function in Drosophila could potentially facilitate studies of how initiation of DNA replication is regulated and coupled to mitosis during metazoan development.