Reproduction: fertilisation: practice question

A Physiology question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Physiology · Reproduction: fertilisation

Sample item

Which event follows the binding of a capacitated sperm to the zona pellucida of the oocyte?

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

D. The acrosome reaction, which releases enzymes such as acrosin and hyaluronidase

Capacitation occurs in the female genital tract and prepares the sperm. Binding to the zona glycoprotein ZP3 triggers the acrosome reaction, releasing hydrolytic enzymes that digest a path through the zona. After fusion with the oocyte membrane, cortical granules are released, the zona hardens and the oocyte completes meiosis II.

Option by option

  • A. The male and female pronuclei fuse to form the zygote nucleus

    Pronuclear fusion happens later, after sperm entry and completion of meiosis II.

  • B. Capacitation begins, with removal of cholesterol from the sperm membrane

    Capacitation takes place before zona binding and is a prerequisite for it.

  • C. The oocyte completes meiosis I and extrudes the first polar body

    Meiosis I of the oocyte finishes just before ovulation under the LH surge, not after sperm binding.

  • D. The acrosome reaction, which releases enzymes such as acrosin and hyaluronidase (correct)

    ZP3 binding triggers exocytosis of acrosomal enzymes, which opens a path through the zona.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

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Questions about this Physiology question

What is the answer to this Physiology question?

The best answer is D, The acrosome reaction, which releases enzymes such as acrosin and hyaluronidase. Capacitation occurs in the female genital tract and prepares the sperm.

Why is "The male and female pronuclei fuse to form the zygote nucleus" not the answer?

Pronuclear fusion happens later, after sperm entry and completion of meiosis II.

Why is "Capacitation begins, with removal of cholesterol from the sperm membr…" not the answer?

Capacitation takes place before zona binding and is a prerequisite for it.

Why is "The oocyte completes meiosis I and extrudes the first polar body" not the answer?

Meiosis I of the oocyte finishes just before ovulation under the LH surge, not after sperm binding.

What concept does this question test?

It tests Reproduction: fertilisation in Physiology. Binding to the zona glycoprotein ZP3 triggers the acrosome reaction, releasing hydrolytic enzymes that digest a path through the zona. After fusion with the oocyte membrane, cortical granules are released, the zona hardens and the oocyte completes meiosis II.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Reproduction: fertilisation?

For each system, sketch the key graph (pressure–volume loop, oxygen dissociation curve, nephron handling) and explain it aloud. Then use the flashcards and the other Physiology questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.