A single cyclin A gene has been identified in Drosophila while Xenopus, mice and humans contain two distinct types of cyclin A: A1, the embryonic-specific form, and A2, the somatic form. Cyclin A1 is prevalently expressed during meiosis and early on in embryogenesis.
A single cyclin A gene has been identified in Drosophila, whereas Xenopus, mice, and humans possess two types of cyclin A: A1, specific to embryonic development, and A2, more widespread in adult tissues. Cyclin A1 is predominantly expressed during meiosis and early stages of development.