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Human Reproduction Set-4 MCQ Online Practice Test | Class 12 | Quiz Tweek

Human Reproduction Set-4

Practice Important MCQs for Human Reproduction — Biology, Class 12.

Human Reproduction is a core Class 12 Biology chapter that links hormonal control, gamete formation, fertilization, pregnancy, and assisted reproductive technologies (ART). It is frequently tested in board exams through conceptual questions on the menstrual cycle and mechanisms like capacitation/cortical reaction, and in competitive exams for endocrine logic (positive/negative feedback), developmental outcomes of fertilization, and application-based problems involving contraception and ART.

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Q1. (In an in vitro assay motility of spermatozoa declines following first‑order kinetics with half‑life $t_{1/2}=3\ \text{h}$ . If initial motility is 80% at $t=0$ , what will be motility after 6 h? Use $M=M_0\,2^{-t/t_{1/2}}$ .)

(A)

10%

(B)

20%

(C)

40%

(D)

60%

Q2. (A woman in her late follicular phase is given an aromatase inhibitor that blocks conversion of androgens to estrogens. Which of the following outcomes in that cycle is most likely?)

(A)

Basal FSH and LH remain unchanged but the pre‑ovulatory LH surge occurs earlier than usual.

(B)

Low estrogen leads to a compensatory LH surge from adrenal estrogens, so ovulation proceeds normally.

(C)

Follicles undergo premature luteinization causing an early rise in progesterone and an early menstruation.

(D)

Serum estrogen falls; the positive feedback required for the pre‑ovulatory LH surge is absent, so the midcycle LH surge does not occur and ovulation fails (anovulatory cycle).

Q3. (In an ART clinic 20 oocytes are retrieved: 8 are at metaphase‑II (MII), 8 at germinal‑vesicle (GV) stage and 4 are degenerated. If in‑vitro maturation (IVM) converts GV → MII at 50% efficiency and intracytoplasmic sperm injection (ICSI) fertilizes MII oocytes with 50% success, use $N_{\text{fert}}=(N_{\text{MII}}+N_{\text{GV}}\times r_{\text{IVM}})\times r_{\text{ICSI}}$ . The expected number of fertilized zygotes is:)

(A)

(B)

(C)

(D)

Q4. (Assertion (A): A genetic defect that renders LH receptors in ovarian theca interna cells nonfunctional will lead to failure of ovulation. Reason (R): LH stimulation of theca cells is necessary for androgen synthesis, and these androgens are aromatized into estradiol by granulosa cells; without LH‑driven androgen production the pre‑ovulatory estradiol rise and consequent LH surge cannot occur, preventing follicular rupture.)

(A)

Both A and R are true, but R does not explain A.

(B)

A is true but R is false.

(C)

Both A and R are true and R correctly explains A.

(D)

A is false but R is true.

Q5. (During normal fertilization the sperm‑oocyte fusion triggers an increase in oocyte cytosolic Ca^{2+}, which induces cortical granule exocytosis and completion of meiosis II. In an experimental IVF trial, oocytes were treated with a membrane‑permeable Ca^{2+} chelator immediately before insemination. Which outcome is most likely?)

(A)

Oocytes will complete meiosis II and form the female pronucleus normally, while cortical granule release will be enhanced.

(B)

Calcium chelation will block cortical granule exocytosis and prevent completion of meiosis II, causing failure of female pronucleus formation and a high risk of polyspermy.

(C)

Calcium chelation will have no effect on polyspermy but will increase sperm capacitation, thus raising fertilization rates.

(D)

Treated oocytes will bypass the need for paternal centrosome and develop normally into diploid embryos by parthenogenesis.

Q6. An ejaculate of volume $2.4\ \mathrm{ml}$ contains $3.0\times10^8$ sperm. What are the sperm concentrations expressed as (i) sperm per millilitre and (ii) sperm per microlitre ( $\mu$ l)?

(A)

$1.25\times10^7\ \text{per ml}$ and $1.25\times10^4\ \text{per}\ \mu\text{l}$

(B)

$7.5\times10^7\ \text{per ml}$ and $7.5\times10^4\ \text{per}\ \mu\text{l}$

(C)

$1.25\times10^8\ \text{per ml}$ and $1.25\times10^5\ \text{per}\ \mu\text{l}$

(D)

$3.0\times10^8\ \text{per ml}$ and $3.0\times10^5\ \text{per}\ \mu\text{l}$

Q7. In an assisted reproduction cycle a woman is pretreated with a GnRH agonist for 10 days to prevent a premature LH surge, then given exogenous FSH for follicular stimulation. After oocyte retrieval and embryo transfer she shows luteal phase insufficiency with low serum progesterone despite multiple corpora lutea. Which of the following best explains her low luteal progesterone?

(A)

Prolonged GnRH agonist treatment causes pituitary desensitisation and reduced LH secretion, resulting in inadequate luteal LH support for corpora lutea

(B)

High estradiol from multiple stimulated follicles exerts negative feedback that directly suppresses progesterone secretion by the corpus luteum

(C)

Exogenous FSH during stimulation permanently impairs luteal cell steroidogenic capacity, lowering progesterone production

(D)

The hCG used for ovulation trigger desensitises luteal cells and thereby reduces progesterone secretion

Q8. In an IVF laboratory experiment washed human sperm, when suspended in physiological saline, regain motility but cannot penetrate the zona pellucida or fertilize an oocyte until albumin is added to the medium. Which is the most likely explanation?

(A)

Albumin supplies an energy substrate required for sperm motility (motility was absent without albumin)

(B)

Albumin binds to the zona pellucida and thereby facilitates sperm–zona binding

(C)

Albumin causes an immediate acrosome reaction so sperm can attach to the oocyte

(D)

Albumin promotes removal of cholesterol from the sperm plasma membrane, allowing capacitation to occur and enabling subsequent acrosome reaction and zona penetration

Q9. Assertion: A 46,XY individual with complete androgen insensitivity syndrome (CAIS) presents with typical female external genitalia, a shortened blind-ending vagina and absence of uterus.
Reason: In CAIS the androgen receptor is nonfunctional so Wolffian duct structures and external masculinisation fail to develop, while Sertoli cell secretion of anti-Müllerian hormone (AMH) causes regression of Müllerian ducts during embryogenesis, preventing uterine development.

(A)

Both assertion and reason are true but the reason does not correctly explain the assertion

(B)

Both assertion and reason are true and the reason correctly explains the assertion

(C)

Assertion is true but the reason is false

(D)

Assertion is false but the reason is true

Q10. A woman with a regular 28‑day cycle ovulates on day 14. Sperm can survive up to $5$ days in the female reproductive tract and an ovum remains fertilisable for about $24$ hours after ovulation. Emergency contraception with levonorgestrel mainly acts by delaying ovulation if taken before the LH surge. She has unprotected intercourse on day 12 and again on day 15. If levonorgestrel is taken within 72 hours after each episode, for which episode is it most likely to prevent pregnancy?

(A)

Prevents pregnancy after intercourse on day 12 but not after intercourse on day 15

(B)

Prevents pregnancy after intercourse on day 15 but not after intercourse on day 12

(C)

Prevents pregnancy after both the day 12 and the day 15 episodes

(D)

Prevents pregnancy after neither episode because sperm can survive for $5$ days

Q11. A semen analysis reports a sperm concentration of $80\times10^6\ \text{mL}^{-1}$ , ejaculate volume $3.5\ \text{mL}$ and progressive motility $60\%$ . The total number of progressively motile spermatozoa in the ejaculate is closest to:

(A)

$2.8\times10^8$

(B)

$1.68\times10^8$

(C)

$4.48\times10^8$

(D)

$1.12\times10^8$

Q12. Letrozole (an aromatase inhibitor) and clomiphene citrate are both used for ovulation induction. Which statement most accurately describes how letrozole induces ovulation compared to clomiphene in terms of circulating estradiol, pituitary gonadotropin release and endometrial effect?

(A)

Letrozole raises circulating estradiol, causing negative feedback and reduced $FSH$ , which prevents follicular recruitment and thins the endometrium.

(B)

Letrozole blocks hypothalamic estrogen receptors, increasing $GnRH$ pulsatility and causing an $LH$ surge, and thins the endometrium similar to clomiphene.

(C)

Letrozole increases local aromatization in granulosa cells producing more estradiol and predisposes to luteal phase defect.

(D)

Letrozole inhibits aromatase, lowering circulating estradiol; the reduced negative feedback increases pituitary $FSH$ to stimulate follicular growth, and because letrozole does not antagonize estrogen receptors like clomiphene, endometrial development is relatively better preserved.

Q13. A 30‑year‑old male with congenital bilateral absence of seminal vesicles has normal testicular histology and serum testosterone but presents with subfertility. Which combination of semen parameter changes best explains his reduced fertility?

(A)

Markedly reduced ejaculate volume, absent seminal fructose, lower (more acidic) $pH$ , normal sperm count but decreased progressive motility

(B)

Normal ejaculate volume, absent seminal fructose, alkaline $pH$ , and reduced sperm count

(C)

Reduced ejaculate volume, compensatory increase in seminal fructose, and preserved progressive motility

(D)

Unchanged ejaculate volume and fructose, but increased prostaglandins causing transient hyperactivated sperm leading to premature death

Q14. Assertion (A): Frequent suckling by the infant maintains high maternal prolactin levels and thereby suppresses ovulation (lactational amenorrhea).
Reason (R): Prolactin suppresses ovulation by directly inhibiting folliculogenesis at the ovarian level, preventing follicle maturation.

(A)

Both A and R are true, and R is the correct explanation of A.

(B)

Both A and R are true, but R is not the correct explanation of A.

(C)

A is true but R is false.

(D)

A is false but R is true.

Q15. During oogenesis, nondisjunction of chromosome 21 occurs. If the resulting gametes are fertilized by a normal sperm (carrying one copy of chromosome 21), what is the probability that the zygote will be trisomic for chromosome 21 when nondisjunction occurred during meiosis I of oogenesis?

(A)

$25\%$

(B)

$50\%$

(C)

$75\%$

(D)

$100\%$

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Human Reproduction Set-4

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