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Human Reproduction Set-5 MCQ Online Practice Test | Class 12 | Quiz Tweek

Human Reproduction Set-5

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

Human Reproduction is a core Class 12 Biology chapter because it links hormonal control, gametogenesis, fertilization, implantation, and genetic concepts (Mendelian ratios, imprinting, chromosomal disorders). Board questions often test both qualitative understanding (hormone roles, events in pregnancy) and quantitative/probability reasoning (IVF success, segregation outcomes), while competitive exams add deeper mechanistic and counselling-based questions.

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Q1. A man's ejaculate has volume $3.5\ \mathrm{mL}$ , sperm concentration $60\times10^6\ \mathrm{mL^{-1}}$ and motility $70\%$ . Estimate the number of motile sperm present in the ejaculate.

(A)

$1.26\times10^8$

(B)

$1.47\times10^8$

(C)

$2.10\times10^8$

(D)

$2.45\times10^7$

Q2. An IVF laboratory receives a semen sample of volume $3\ \mathrm{mL}$ with sperm concentration $80\times10^6\ \mathrm{mL^{-1}}$ and motility $60\%$ . After swim‑up selection only $20\%$ of the initial motile sperm are recovered as usable motile sperm. If conventional IVF protocol requires $1\times10^5$ motile sperm per oocyte, approximately how many oocytes can be inseminated from this processed sample?

(A)

$144$

(B)

$2\,880$

(C)

$72$

(D)

$288$

Q3. A couple, both carriers for an autosomal recessive disorder, produce four embryos by IVF that reflect the Mendelian genotypic ratio $1:2:1$ (AA : Aa : aa). Two embryos are randomly chosen for transfer. What is the probability that both transferred embryos are free of the disease genotype (i.e., are AA or Aa)?

(A)

$50\%$

(B)

$25\%$

(C)

$75\%$

(D)

$33.3\%$

Q4. In preimplantation genetic diagnosis (PGD) a blastocyst's trophectoderm has $100$ cells, $30\%$ of which are aneuploid and randomly distributed. A biopsy samples $5$ trophectoderm cells at random. The probability that the biopsy detects at least one aneuploid cell equals $1-\prod_{i=0}^{4}\dfrac{70-i}{100-i}$ . Approximately what is this detection probability?

(A)

$\approx 16\%$

(B)

$\approx 60\%$

(C)

$\approx 84\%$

(D)

$\approx 96\%$

Q5. Sertoli cells secrete androgen‑binding protein (ABP) to concentrate testosterone in seminiferous tubules for spermatogenesis. Consider a man whose Sertoli cells cannot produce ABP but whose Leydig cells and circulating testosterone are normal. Which of the following best describes the expected clinical and hormonal profile?

(A)

Severe oligospermia with normal serum testosterone, raised $FSH$ , normal $LH$ , but reduced secondary sexual characters

(B)

Oligozoospermia (low sperm count), raised $FSH$ , normal $LH$ , normal serum testosterone and normal secondary sexual characteristics

(C)

Oligozoospermia with normal serum testosterone, low $FSH$ , normal $LH$ , and normal secondary sexual characteristics

(D)

High sperm count with low $FSH$ , elevated $LH$ and signs of androgen excess

Q6. In a man's ejaculated sperm population, $60\%$ of sperm carry an X chromosome and $40\%$ carry a Y chromosome. If he fertilizes a normal XX woman's oocyte (which always provides an X), what is the probability that the resulting child will be male?

(A)

$50\%$

(B)

$60\%$

(C)

$40\%$

(D)

$20\%$

Q7. A secondary oocyte fails to extrude the second polar body after completion of meiosis II and is then fertilized by a normal haploid sperm. What will be the chromosomal constitution (ploidy and approximate chromosome count) of the resulting zygote?

(A)

$3n = 69$

(B)

$2n = 46$

(C)

$n = 23$

(D)

$4n = 92$

Q8. A 30-year-old infertile male has testicular biopsy showing seminiferous tubules containing only Sertoli cells while Leydig cells appear histologically normal. Which endocrine profile is most consistent with this finding?

(A)

$FSH$ : normal, $LH$ : high, $T$ : low, $Inhibin\ B$ : normal

(B)

$FSH$ : high, $LH$ : high, $T$ : low, $Inhibin\ B$ : low

(C)

$FSH$ : high, $LH$ : low, $T$ : low, $Inhibin\ B$ : low

(D)

$FSH$ : high, $LH$ : normal, $T$ : normal, $Inhibin\ B$ : low

Q9. A woman is a carrier of a balanced Robertsonian translocation rob(14;21). Assuming all meiotic segregation products are equally likely but zygotes with monosomy of chromosome 14 or 21 are lethal and do not survive to term, what fraction of the surviving (liveborn) offspring is expected to have trisomy 21 (Down syndrome)?

(A)

$\dfrac{1}{6}$

(B)

$\dfrac{1}{3}$

(C)

$\dfrac{1}{2}$

(D)

$\dfrac{2}{3}$

Q10. A mutation makes the $LH$ receptor in ovarian theca interna constitutively active so it signals continuously without $LH$ . Which long-term effects on the menstrual cycle and endometrium are most likely?

(A)

Chronic androgen overproduction (↑ androstenedione/testosterone), suppression of $FSH$ by negative feedback, anovulation/oligomenorrhea, and endometrial proliferation with risk of hyperplasia due to unopposed estrogen

(B)

Increased frequency of ovulation (multiple ovulations per cycle), raised progesterone output and a markedly secretory endometrium

(C)

Markedly reduced ovarian steroidogenesis causing hypoestrogenism, amenorrhea and endometrial atrophy

(D)

Normal ovulation with decreased androgens and consistently normal luteal phases due to compensatory ovarian changes

Q11. In human spermatogenesis each primary spermatocyte gives rise to $4$ haploid spermatozoa after meiotic divisions. In a steady state the testes release $480\times10^6$ sperm per day; assuming no loss during maturation, the minimum number of primary spermatocytes that must complete meiosis per day to sustain this output is:

(A)

$480\times10^6$ primary spermatocytes per day

(B)

$240\times10^6$ primary spermatocytes per day

(C)

$120\times10^6$ primary spermatocytes per day

(D)

$60\times10^6$ primary spermatocytes per day

Q12. A couple undergoes intracytoplasmic sperm injection (ICSI) because the male partner has severe oligozoospermia due to a microdeletion in the AZFc region of his Y chromosome. Which of the following statements most accurately describes the likely genetic/clinical consequence and an appropriate counselling point?

(A)

Male offspring conceived via ICSI will inherit the father's Y‑chromosome microdeletion and are likely to have impaired spermatogenesis; female offspring will not inherit the Y deletion.

(B)

ICSI corrects Y‑chromosome microdeletions during fertilization, so offspring will not inherit the deletion.

(C)

Both male and female offspring will inherit the Y‑chromosome microdeletion.

(D)

Using any sperm from the same ejaculate eliminates the risk of transmitting the deletion because only some sperm carry the defect.

Q13. Neutralizing anti‑hCG antibodies are administered to a pregnant woman in two separate scenarios: once at gestational week $5$ and once at gestational week $12$ . Predict the most likely outcome for each pregnancy.

(A)

Both pregnancies will terminate because neutralizing hCG always causes corpus luteum regression.

(B)

Neither pregnancy will be affected since the placenta produces adequate progesterone after implantation.

(C)

The pregnancy treated at week $12$ will terminate but the one treated at week $5$ will continue.

(D)

The pregnancy treated at week $5$ will most likely terminate while the one treated at week $12$ will continue, because the placenta assumes progesterone production by approximately weeks $8$ -- $10$ .

Q14. Regarding intrauterine devices (IUDs) and ectopic pregnancy risk, which statement best captures the correct epidemiological and mechanistic relationship?

(A)

Use of an IUD increases the absolute risk of ectopic pregnancy compared with using no contraception.

(B)

An IUD reduces the overall (absolute) risk of pregnancy — including ectopic pregnancy — but among the small number of pregnancies that occur with an IUD in place, the probability that the pregnancy is ectopic is higher than among pregnancies in non‑users.

(C)

An IUD does not change the proportion of ectopic pregnancies among pregnancies that occur; it only changes the absolute number of pregnancies.

(D)

Copper IUDs prevent ectopic pregnancy by acting mainly in the uterus to block implantation, so ectopic pregnancies are less likely among users than in non‑users.

Q15. Artificial activation of mammalian oocytes (parthenogenesis) can induce cleavage and sometimes blastocyst‑like formation, yet viable offspring are not produced. Which explanation best accounts for this failure in mammals?

(A)

Oocyte‑derived maternal mRNAs are exhausted by the $2$ ‑cell stage so development cannot continue without sperm contribution.

(B)

Parthenogenetic embryos lack centrioles/centrosomes normally contributed by the sperm, so mitotic division fails early.

(C)

Genomic imprinting — absence of the paternal genome and its paternal imprints leads to abnormal extra‑embryonic (placental) development, preventing viable offspring.

(D)

Parthenogenetic embryos are rejected by the maternal immune system because they lack paternal antigens required to induce immune tolerance.

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