Question: Which of the following is true for first and second meiotic divisions of oogonia?
A 1st meiotic division is completed at puberty, 2nd meiotic division is completed prior to sperm entry into the cytoplasm of ovum
B Both 1st and 2nd meiotic divisions are completed after the entry of sperm into the cytoplasm of ovum
C 1st meiotic division is completed after the entry of sperm, 2nd meiotic division is completed during implantation
D 1st meiotic division is completed prior to ovulation, 2nd meiotic division is completed after the entry of sperm into the cytoplasm of ovum.
Answer: 1st meiotic division is completed prior to ovulation, 2nd meiotic division is completed after the entry of sperm into the cytoplasm of ovum.
| Aspect | Meiosis I | Meiosis II |
| Introduction | Occurs during fetal development and is usually completed prior to a female’s birth. | Occurs after fertilization, during the process of oocyte activation and usually after the entry of sperm into the cytoplasm of the ovum. |
| Oocyte Stage | Primary oocyte | Secondary oocyte |
| Chromosomes | Diploid (2n) | Haploid (n) |
| Result | Produces one secondary oocyte and one polar body. | Produces a mature ovum (egg) and another polar body. |
| Completion | Pauses at prophase I, resumes at ovulation and halts again at metaphase II. | Pauses at metaphase II until fertilization occurs, then completes if fertilization happens. |
| Significance | Reduces chromosome number by half, creating genetic diversity and preparing for fertilization. | Facilitates the formation of a mature, haploid ovum capable of uniting with a sperm to form a diploid zygote. |