When do primary oocytes complete Meiosis I?

• A. During menopause
• B. At birth
• C. During fertilization
• D. During puberty

Answer: (D)

Verified step by step guidance

1. Understand that oogenesis is the process of forming mature egg cells (ova) in females, which begins before birth and continues until menopause.
2. Recognize that primary oocytes are formed during fetal development and are arrested in prophase I of meiosis until puberty.
3. At puberty, hormonal changes trigger the continuation of meiosis in a select number of primary oocytes during each menstrual cycle.
4. During each cycle, one primary oocyte completes Meiosis I to form a secondary oocyte and a polar body.
5. The secondary oocyte then begins Meiosis II, which is only completed if fertilization occurs.