Question

In human females, meiosis II is not completed until
A. Birth
B. Puberty
C. Fertilization
D. Uterine implantation

Answer 1

In human females, the secondary oocyte is arrested in a metaphase-II stage until sperm cell contacts the plasma membrane of the oocyte and completes meiosis II resulting in the release of the ovum. It is a major event of the reproduction process.

Complete answer: The meiosis-II stage is completed in oogenesis only after fertilization. When sperm enters the egg cell, the centrioles from the sperms allow the spindle formation and the completion of the meiosis-II stage occurs. This is further accompanied by nuclear fusion and ultimately results in the formation of a zygote. The fertilization is the fusion of haploid gametes, an egg and the sperm to form a diploid zygote. Though, there can be subtle differences in the fertilization process which occurs naturally within the body or through the reproductive technologies outside the body, the overall product in both cases is a diploid zygote. The sperm and the egg are called gametes. They each contain half the genetic information necessary for the reproduction. When the sperm cell penetrates and fertilizes an egg, the genetic information combines. Doctors refer fertilized eggs as embryo after implantation.
Hence, the correct answer is option C.

Note: The fertilization occurs when a sperm and an egg have fused together to form a zygote, which begins to divide as it moves towards the uterus. Women may experience cramps very early in pregnancy. These are due to the implantation, which is when the fertilized egg attaches to the lining of the uterus.