NEET Zoology - MCQ Practice Questions

Folic acid supplementation (400 mcg minimum, higher for high-risk women) during the periconceptional period reduces neural tube defects by 50-70%.

Ovulation typically occurs 14 days before the next menstruation. In a 28-day cycle, this corresponds to day 14 of the cycle, marking the middle of the proliferative phase.

The LNG-IUD releases levonorgestrel directly into the uterine cavity, causing endometrial atrophy and thickened cervical mucus, with effectiveness lasting 3-7 years.

FSH directly stimulates Sertoli cells in seminiferous tubules to initiate spermatogenesis. While LH and testosterone support the process, FSH is the primary initiator.

Spermicides used alone have a failure rate of 18-28% with typical use. IUDs and implants have failure rates <1% with typical use.

The secondary oocyte is arrested in metaphase II at ovulation. It completes meiosis II only if fertilization occurs.

Chlamydia trachomatis is the leading cause of PID, accounting for 30-40% of cases. Neisseria gonorrhoeae is the second most common cause.

In a 28-day cycle, ovulation typically occurs on day 14. The fertile window includes 5 days before and 1 day after ovulation (approximately days 8-19), accounting for sperm survival and ovum viability.

Copper T 380A has the longest duration of effectiveness (10-12 years) among copper IUDs approved in India, with the lowest failure rate of 0.6-0.8%.

The luteal phase is characterized by high progesterone levels secreted by the corpus luteum. Estrogen levels are moderate but lower than follicular phase peak.