Question

During Oogenesis why does the Oocyte arrest its cell division at various places, why can't it form an ovum straight away?

Answer 1

Oogenesis:

1. Oogenesis is the process through which female gametes are formed.
2. In contrast, in placental mammals, the egg ceases to be referred to be an egg once it has been fully formed and fertilized and has started to divide. We must keep in mind that each ovum must be haploid and contain one copy of each chromosome.

Arresting of cell division at oocyte:

1. The division can be stopped, giving the egg access to every resource it might possibly require.
2. Oocytes actively translate and transcribe during the first arrest stage (diplotene stage of the first meiotic division).
3. Chromosomes are also decondensed as a result to support transcription.
4. The oocyte is again paused at metaphase II during meiosis II, after the polar body I have developed, while it awaits the sperm in the fallopian tube and, potentially, the completion of meiosis II, which results in the formation of the ovum and, finally, the zygote.