Final answer:
Oogenesis begins before birth when an oogonium undergoes mitosis and produces a primary oocyte.
Step-by-step explanation:
Oogenesis is the process by which female gametes, known as eggs or ova, are produced in the ovaries. It is a crucial part of the female reproductive system and involves a series of complex events that occur throughout a woman's life, beginning before birth and continuing until menopause.
Oogenesis begins long before birth when an oogonium with the diploid number of chromosomes undergoes mitosis. It produces a diploid daughter cell called a primary oocyte. The primary oocyte, in turn, starts to go through the first cell division of meiosis.