The gametes originate in the yolk sac and migrate to the gonads in the form of primordial germ cells.
The primordial germ cells transform into either sperm or ova depending on the individual’s sex.
This phase begins with oogonia in females and spermatogonia in males; both types of cells have 46 chromosomes and 2 NDNA.
Meiosis I concludes with the formation of secondary gametocytes (23, 2 N).
Processes occurring during meiosis I are DNA replication and crossing over.
Note: The centromere does not divide during meiosis I.