Question

How many meiotic divisions are required for the formation of 50 zygotes?
A. 62
B. 63
C. 61
D. 50

Answer 1

Meiotic division is the process of cell division occurring in the germ cells of organisms that sexually reproduce. This cell division is involved in the production of gametes such as eggs or sperm that contain half the number of chromosomes in the somatic cells.

Complete answer:
Meiosis involves two rounds of division. First division will separate the pairs of homologous chromosomes into half. The second division results in separation of the sister chromatids, which is created by the replication of DNA during interphase. The process, however, is slightly different for males and females gametes.

In male gametes, the meiosis occurs during spermatogenesis, which is the development of haploid spermatozoa (n) from the germ cells. The first division gives two spermatocytes, which further divides into two, giving four spermatozoa. Thus, four spermatozoa (n) are produced in one meiosis.
In case of female gametes, it is quite straightforward, as one meiotic division in oogenesis produces a single egg (n).

Now that we found the number of gametes produced through each meiotic division for both male and female gametes, let us calculate the number of meiotic divisions needed for the formation of 50 zygotes. A zygote is diploid (2n) in nature and is formed during the fertilization of male gamete with the female gamete. For 50 zygotes, 50 male and 50 female gametes are required. Therefore, 13 meiotic divisions during spermatogenesis produce 52 sperms and 50 meiotic divisions during oogenesis produces 50 eggs.

Hence, the correct answer is option (B).

Additional information:
- Meiosis I has four phases just like mitosis (Prophase, Metaphase, Anaphase, and Telophase) with some small differences. The result that is acquired from meiosis 1 are two diploid cells having genetic differences that are present on the chromosomes as these result in the crossing- over.
- The crossing over is the process that occurs after both the homologous chromosomes join to form a structure called tetrad.
- The tetrads are formed through the process called synapsis and once a tetrad is formed, a portion of each homologous chromosome breaks and reattaches to the same part of homologue.
- This allows the mixing up of the traits that is present in each chromosome thus resulting in genetic recombination.

Note: Meiotic division is crucial for the formation of zygote, as it eventually becomes the fetus in humans. If any error occurs during the division, it results in aneuploidy, which is the presence of an abnormal number of chromosomes in the cell. This condition causes development disabilities or sometimes leads to miscarriage of the fetus itself.