Human Reproduction Set-1

Q1. A spermatozoon swims at an average speed of $v = 3\ \text{mm/min}$ from the vaginal opening toward the ampullary region; the straight-line distance is approximately $d = 150\ \text{mm}$. Assuming constant speed and no delays, how long will it take to reach the ampulla?

Q2. A woman has regular menstrual cycles of length $32$ days. Using the rule that ovulation occurs about $14$ days before the next menses, and given that sperm can survive up to $5$ days in the female tract while the ovum is viable for about $24$ hours after ovulation, which days of her cycle (day 1 = first day of menstrual bleeding) constitute the most likely fertile window?

Q3. A mutation renders LH receptors on Leydig cells nonfunctional in a male patient. Which pattern of steady-state serum hormone levels relative to normal is the most likely outcome?

Q4. Assertion (A): The risk of aneuploidy due to nondisjunction in human oocytes increases with maternal age.
Reason (R): Cohesin complexes that maintain sister chromatid cohesion during the prolonged prophase I arrest of oocytes deteriorate over time, increasing the probability of segregation errors when meiosis resumes.

Q5. A 17-year-old phenotypic female is found to have a $46,XY$ karyotype and undescended testes on imaging; she has normal breast development but scant pubic/axillary hair and a blind-ending vaginal pouch. Which of the following combinations of findings is most consistent with complete androgen insensitivity syndrome (CAIS)?

Q6. A semen sample has an ejaculate volume of $3\ \text{mL}$ and a sperm concentration of $60\times10^6\ \text{sperm/mL}$. If only $0.1\%$ of sperm reach the cervical canal after ejaculation, approximately how many sperm reach the cervix?

Q7. An early embryo begins secreting hCG after implantation. If serum hCG at implantation (day 0) is $8\ \text{mIU/mL}$ and it doubles every $48\ \text{h}$ (so $hCG(t)\approx 8\times 2^{t/2}$ with $t$ in days), and a urine pregnancy test requires $\ge 25\ \text{mIU/mL}$ to turn positive, approximately how many days after implantation will the test become positive?

Q8. In an IVF cycle two embryos are transferred and each embryo implants independently with probability $0.40$. What is the probability that the patient will have a twin gestation (both embryos implant)?

Q9. Assertion (A): A copper intrauterine device (Cu–IUD) primarily prevents pregnancy by blocking implantation of a fertilized ovum.
Reason (R): Copper ions ($\mathrm{Cu^{2+}}$) released from the device are toxic to sperm and also elicit a local sterile inflammatory reaction in the endometrium, creating an environment hostile to gametes and fertilization.
Choose the correct option:

Q10. A woman has a genetic mutation that renders LH receptors on the theca interna cells nonfunctional. Which of the following best describes the expected hormonal profile and ovarian outcome?