This happens during spermatogenesis

The correct option is Meiosis and mitosis.

Spermatogenesis is the biological process by which male gametes (spermatozoa) are produced in the testes from immature germ cells. This complex developmental process involves both mitotic and meiotic cell divisions to ensure both the renewal of the stem cell population and the production of haploid sperm cells.

Let's break down the stages of spermatogenesis step-by-step to understand why both type of divisions occur:
1. Mitosis (Spermatogonial Phase): The process begins with diploid stem cells called spermatogonia (2n) located at the basement membrane of the seminiferous tubules. These cells undergo mitotic division (mitosis) to multiply and maintain their own population (self-renewal). Some of the daughter cells resulting from this mitotic division differentiate into primary spermatocytes (2n). Since mitosis maintains the original chromosome number, this step ensures a continuous supply of germ cells.
2. Meiosis (Spermatocyte Phase): Each diploid primary spermatocyte (2n) then enters meiosis. Meiosis consists of two successive nuclear divisions:
- Meiosis I: The primary spermatocyte undergoes the first meiotic division to produce two haploid secondary spermatocytes (n).
- Meiosis II: Each secondary spermatocyte quickly undergoes the second meiotic division, resulting in a total of four haploid spermatids (n).
3. Spermiogenesis: The spermatids undergo a maturation process (without further cell division) to transform into functional, motile spermatozoa (sperm cells).

Therefore, because the entire sequence of spermatogenesis requires mitotic division for stem cell proliferation and meiotic division for reducing the chromosome number to half, both meiosis and mitosis take place during this process.