when do oogonia undergo mitosis?
a. before birth
b. at puberty
c. during fertilization
d. at the beginning of each menstrual cycl
The Correct Answer and Explanation is :
The correct answer is a. before birth.
Explanation:
Oogonia are the precursor cells that develop into oocytes (egg cells) in the female reproductive system. The process of oogenesis, which is the formation of ova, begins early in fetal development. During the first trimester of pregnancy, specifically around the 6th to 7th week, primordial germ cells migrate to the developing ovaries and differentiate into oogonia. These oogonia are diploid cells, meaning they contain two sets of chromosomes.
Once in the ovaries, oogonia undergo several rounds of mitotic division. This proliferation is crucial as it increases the number of oocytes available for future development. By around 20 weeks of gestation, the number of oogonia peaks, reaching approximately 7 million. However, as gestation progresses and by the time of birth, many of these oogonia undergo apoptosis (programmed cell death), leaving about 1 to 2 million primary oocytes at birth. These primary oocytes enter a stage of development known prophase I of meiosis and become arrested in this phase until puberty.
After birth and until puberty, no further mitotic divisions of oogonia occur. Instead, the primary oocytes remain in this dormant state within the ovarian follicles. It’s only during puberty, in response to hormonal changes, that the primary oocytes resume meiosis and are released during the menstrual cycle as secondary oocytes.
Therefore, the key period for oogonia to undergo mitosis is before birth, making option (a) the correct choice. This early phase is essential for establishing the initial pool of eggs that will be available for fertilization throughout a woman’s reproductive life.