Question

The second maturation division of the mammalian ovum occurs

• A. In the Graafian follicle following the first maturation division.
• B. Shortly after ovulation before the ovum makes entry into the fallopian tube.
• C. Until after the ovum has been penetrated by a sperm.
• D. Until the nucleus of the sperm has fused with that of the ovum.

Answer 1

The correct option is C Until after the ovum has been penetrated by a sperm.

The nearly mature oocyte is called as ootid, where the first meiotic division has been completed and the second initiated. However, in most of the higher mammals, including humans, the second meiotic division is not completed unless fertilization occurs i.e., until the egg has been penetrated by a sperm. Therefore, the ootid contains two separate haploid elements, male and femal pronuclei and when they fuse, it results in the formation of zygote.