Which of the following events does NOT lead to genetic variation?

Correct Answer: D

Rationale: The correct answer is D. Crossing over between homologous chromosomes during meiosis II does not lead to genetic variation. This is because crossing over occurs during meiosis I, not meiosis II. Meiosis II is when the separated chromatids are pulled apart to form haploid cells. Independent assortment of chromosomes during meiosis (A) and random fertilization between ovum and sperm (B) both contribute to genetic variation by creating unique combinations of alleles. Crossing over between homologous chromosomes during meiosis I (C) also leads to genetic variation by exchanging genetic material between homologous chromosomes.

Correct Answer: D

Rationale: Correct Answer: D - Trichomoniasis Rationale: Trichomoniasis is a sexually transmitted infection that commonly presents with vaginal discharge. The discharge is typically frothy, yellow-green, and has a strong odor. This distinguishes it from other causes of vaginal discharge. Summary of Other Choices: A: Vulvovaginal candidiasis - Typically presents with thick, white, cottage cheese-like discharge. B: Granuloma inguinale - Rare bacterial infection causing painless genital ulcers, not associated with vaginal discharge. C: Gonorrhea - May cause vaginal discharge, but typically associated with other symptoms like pelvic pain and abnormal bleeding.

Correct Answer: C

Rationale: The correct answer is C: seminiferous tubule. Spermatogenesis is the process of sperm production and occurs within the seminiferous tubules of the testes. These tubules contain specialized cells called germ cells that undergo meiosis to produce sperm. The tunica albuginea is a fibrous layer surrounding the testes, the rete testis is a network of tubules where sperm is transported, and the seminal vesicle is a gland that produces seminal fluid, not involved in sperm production. Therefore, the seminiferous tubule is the correct choice for spermatogenesis.

Correct Answer: C

Rationale: The correct answer is C: semen. Semen is the fluid that contains spermatozoa, alkaline mucus, and fructose. Spermatozoa are the male reproductive cells, alkaline mucus helps neutralize vaginal acidity, and fructose provides energy for sperm. Semen is the combination of these components, making it the term that encompasses all the other terms listed. A: spermatozoa is incorrect because it is just one component of semen. B: alkaline mucus is incorrect as it is a separate component in semen. D: fructose is incorrect because it is also just one component found in semen.

Correct Answer: C

Rationale: The correct answer is C: zona pellucida. The zona pellucida is the glycoprotein layer surrounding the oocyte. It plays a crucial role in fertilization by binding sperm and facilitating the acrosome reaction. The theca interna and externa are layers surrounding the ovarian follicle, not the oocyte itself. The antrum is a fluid-filled cavity within the follicle, not the outer layer of the oocyte. Therefore, the correct choice is C as it directly relates to the outer layer of the oocyte.