Free MCAT-style practice, 2C
MCAT Reproductive Hormones and Gametogenesis Practice Questions
Eight free MCAT-style practice questions on spermatogenesis, oogenesis arrest points, FSH and LH actions, the ovarian cycle, ovulation timing and hCG, with full explanations.
Quick concept primer
Gametogenesis turns diploid germ cells into haploid gametes. In the testis, each primary spermatocyte finishes meiosis I to give two secondary spermatocytes and meiosis II to give four spermatids, which mature into sperm. In the ovary, primary oocytes enter meiosis I before birth and pause in prophase I. Each cycle, one finishes meiosis I just before ovulation, producing a secondary oocyte and a small polar body; the secondary oocyte then pauses in metaphase II and completes meiosis only if a sperm enters it. Uneven cytoplasm division gives one large egg per primary oocyte.
GnRH from the hypothalamus drives FSH and LH from the anterior pituitary. In males, LH stimulates Leydig cells to make testosterone, and FSH acts on Sertoli cells, which support developing sperm and release inhibin to curb FSH. In females, FSH grows follicles, rising estrogen triggers an LH surge, the surge causes ovulation, and the corpus luteum then secretes progesterone.
Traps: LH goes to Leydig cells, FSH to Sertoli cells; the ovulated cell is a secondary oocyte, not a finished ovum; menstruation follows a fall in progesterone, not the LH surge. The 2C Cell Division, Development and Reproduction pack adds flashcards and more practice across the whole category, and you can try a free sampler first.
8 practice questions
Question 1
A man enrolled in a drug trial receives a compound that selectively blocks luteinizing hormone receptors in the testis. Which change is expected as the most direct result?
- Sertoli cells stop secreting inhibin.
- Pituitary FSH secretion falls.
- Leydig cells increase testosterone secretion.
- Leydig cells decrease testosterone secretion.
Show answer and explanation
Answer: D. Leydig cells decrease testosterone secretion.
Leydig cells carry the LH receptors and make testosterone in response to LH, so blocking those receptors lowers testosterone directly. With less testosterone, negative feedback weakens and FSH and LH would rise, not fall. Inhibin comes from Sertoli cells, which respond mainly to FSH, so blocking LH receptors does not directly stop it.
Question 2
In a model calculation, 500 primary spermatocytes and 500 primary oocytes each complete both meiotic divisions. How many spermatids and how many mature eggs result?
- 2000 spermatids and 1000 eggs
- 2000 spermatids and 500 eggs
- 1000 spermatids and 500 eggs
- 500 spermatids and 500 eggs
Show answer and explanation
Answer: B. 2000 spermatids and 500 eggs
Each primary spermatocyte yields four spermatids, so 500 × 4 = 2000. Each primary oocyte yields only one egg because the divisions are unequal and the other products become polar bodies, so 500 × 1 = 500. The 1000 egg answer treats oogenesis like a single even split, and 1000 spermatids counts only meiosis I.
Question 3
How many chromosomes and how many chromatids are present in a single human secondary spermatocyte before it begins meiosis II?
- 23 chromosomes and 46 chromatids
- 46 chromosomes and 92 chromatids
- 23 chromosomes and 23 chromatids
- 46 chromosomes and 46 chromatids
Show answer and explanation
Answer: A. 23 chromosomes and 46 chromatids
Meiosis I separates homologous chromosomes, so each secondary spermatocyte has 23 chromosomes, but sister chromatids are still joined, giving 2 × 23 = 46 chromatids. Ninety-two chromatids describes a primary spermatocyte after S phase, and 23 single chromatids describes a spermatid after meiosis II.
Question 4
A follicle ruptures and releases its germ cell on day 15 of a woman's cycle. No sperm are present. Which description best fits the released cell?
- A primary oocyte arrested in prophase I
- A mature ovum that has completed meiosis II
- A secondary oocyte arrested in metaphase II
- An oogonium that has not entered meiosis
Show answer and explanation
Answer: C. A secondary oocyte arrested in metaphase II
Meiosis I finishes just before ovulation, so the cell released is a secondary oocyte, and it stays arrested in metaphase II unless a sperm enters and triggers completion of meiosis II. A primary oocyte is the cell that waits in prophase I before the cycle, there is no completed ovum without fertilization, and oogonia stop dividing before birth.
Question 5
The mid-cycle LH surge has each of the following effects EXCEPT:
- triggering rupture of the dominant follicle.
- causing the endometrial lining to shed.
- prompting the dominant follicle's oocyte to complete meiosis I.
- converting the ruptured follicle into the corpus luteum.
Show answer and explanation
Answer: B. causing the endometrial lining to shed.
The LH surge drives ovulation, completion of meiosis I and luteinization of the follicle into the corpus luteum. The endometrium sheds roughly two weeks later, when the corpus luteum regresses and progesterone and estrogen fall. Shedding is caused by hormone withdrawal, not by the LH surge.
Question 6
A student plots illustrative hormone values from one 28-day cycle.
| Cycle day | Estradiol (pg/mL) | Progesterone (ng/mL) | LH (IU/L) |
|---|---|---|---|
| 3 | 40 | 0.5 | 6 |
| 12 | 250 | 0.8 | 10 |
| 14 | 180 | 1.5 | 55 |
| 21 | 150 | 12 | 5 |
Which day best reflects a phase dominated by an active corpus luteum?
- Day 3
- Day 12
- Day 14
- Day 21
Show answer and explanation
Answer: D. Day 21
The corpus luteum secretes large amounts of progesterone with moderate estrogen, and the table shows progesterone peaking at 12 ng/mL on day 21 while LH is low. Day 3 is the early follicular phase, day 12 shows the estrogen rise from a growing follicle, and day 14 shows the LH surge around ovulation, before a corpus luteum has formed.
Question 7
A woman has regular 32-day cycles. Assuming her luteal phase lasts 14 days and day 1 is the first day of menstruation, on about which cycle day does she ovulate?
- Day 14
- Day 16
- Day 18
- Day 21
Show answer and explanation
Answer: C. Day 18
The luteal phase runs from ovulation to the next menstruation and is the more constant part of the cycle, so ovulation falls at 32 − 14 = day 18. Day 14 assumes every cycle is 28 days long, day 16 is half of 32, and day 21 has no basis in the numbers given.
Question 8
In the first weeks of pregnancy, the corpus luteum keeps secreting progesterone instead of regressing. What is mainly responsible?
- Human chorionic gonadotropin from the trophoblast, which acts like LH on the corpus luteum
- A rise in pituitary FSH that stimulates the corpus luteum
- Placental progesterone, which is already sufficient from the day of implantation
- A second LH surge triggered by high estrogen
Show answer and explanation
Answer: A. Human chorionic gonadotropin from the trophoblast, which acts like LH on the corpus luteum
The trophoblast of the implanted embryo secretes hCG, which binds LH receptors and rescues the corpus luteum so progesterone keeps the endometrium intact. FSH does not maintain the corpus luteum, the placenta takes over progesterone production only later in the first trimester, and high progesterone suppresses rather than triggers another LH surge.