Question 1

How many functional ova are produced from one primary oocyte?

Accepted Answer

Only one. Unequal cytokinesis channels nearly all cytoplasm into a single ovum; the polar bodies are tiny, non-functional cells: the second polar body comes from meiosis II, and NCERT leaves it uncertain whether the first polar body divides again or degenerates. NCERT's figure shows two polar bodies, but only one cell ever becomes the functional ovum.

Question 2

When does oogenesis begin in humans?

Accepted Answer

During foetal life. Oogonia multiply and enter meiosis I to become primary oocytes before birth, and no new oogonia are formed after birth. Primary oocytes then remain arrested in prophase I; each one resumes only when it is recruited in a later cycle, which can be decades after birth.

Question 3

What is a polar body?

Accepted Answer

A polar body is the tiny cell produced during the unequal divisions of oogenesis. It receives almost no cytoplasm and carries a haploid nucleus; the second polar body comes from meiosis II, and NCERT leaves it uncertain whether the first divides again or degenerates. Its formation is what allows one primary oocyte to yield a single nutrient-rich ovum.

Question 4

When does the secondary oocyte complete meiosis II?

Accepted Answer

Only if fertilisation occurs. The secondary oocyte is ovulated while arrested at metaphase II; entry of a sperm triggers completion of meiosis II, producing the ovum and the second polar body.

Question 5

What is the difference between Sertoli cells and Leydig cells?

Accepted Answer

Sertoli cells are nurse cells inside the seminiferous tubules that nourish developing sperm and are stimulated by FSH. Leydig (interstitial) cells lie outside the tubules and secrete testosterone (androgens) under the influence of LH.

Spermatogenesis vs Oogenesis: Four Versus One

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