The event where mitosis will NOT take place is D. Gamete formation.

Mitosis is the process of cell division that results in the production of two identical daughter cells, each having the same number of chromosomes as the parent cell. It is involved in various biological processes, including growth, tissue repair, and asexual reproduction.

However, in the case of gamete formation, a specialized type of cell division called meiosis takes place instead of mitosis. Meiosis involves two rounds of cell division and results in the production of gametes (sperm and egg cells) with half the number of chromosomes as the parent cell. This reduction in chromosome number is necessary for sexual reproduction and the formation of genetically diverse offspring.

Therefore, gamete formation does not involve mitosis but rather meiosis.