Question

Under what circumstances does a secondary oocyte complete meiosis II?

A) Upon entering the uterine tube
B) In response to the LH surge at ovulation
C) Upon reaching the uterus
D) In response to stimulation by FSH during the second week of the menstrual cycle
E) Upon fertilization

Answer 1

A secondary oocyte completes meiosis II only upon fertilization by a sperm in the Fallopian tube, leading to the formation of a diploid zygote(option e).

Step-by-step explanation:

A secondary oocyte completes meiosis II under one key circumstance: fertilization by a sperm.

After ovulation, the secondary oocyte may be fertilized by sperm as it travels through the Fallopian tube. Upon successful fertilization, the oocyte quickly finishes meiosis II to form a diploid zygote and another polar body, which usually disintegrates. On the other hand, if the secondary oocyte is not fertilized, it never completes meiosis II and will disintegrate, often while still in the Fallopian tube or at most within a few days after arriving in the uterus, to be expelled during the menstrual cycle.