Hello everyone. Today we are going to talk about cell divisions. These divisions are essential to allow the growth, development, cellular renewal, or reproduction of an individual. In this video, we will detail the mechanisms of mitosis and the mechanisms of meiosis. If you haven't done so yet, I invite you to watch my previous video on genetic information. Come on, let's go! [Music] The meeting of a sperm and an egg will give rise to an egg cell. It is the first cell in our body. This cell will carry out successive divisions to form approximately 30 trillion cells that make up your body. This is mitosis. Mitosis is a process of cell division which makes it possible to produce genetically identical daughter cells from a mother cell . Mitosis allows for the growth, development and cellular renewal of an individual. A human cell has 46 chromosomes. But to detail the mechanism of mitosis in a more understandable way, we will study a method in a cell with two chromosomes. Chromosome pair 1 is made up of a single blue chromosome and a single green chromosome. To prepare for division, the cell will duplicate its genetic material. The amount of genetic material will double, but not the number of chromosomes. The two single chromosomes become two double chromosomes. After duplication, the double chromosomes will line up in the center of the nucleus. The cell will then divide. Each double chromosome separates into two identical single chromosomes, which will be distributed in the two daughter cells. [Music] If we summarize, the mother cell will give two identical daughter cells. After having focused on the phenomenon of mitosis, we will now focus on the phenomena of meiosis. Once an adult, an individual can produce gametes, that is to say reproductive cells: sperm in men and eggs in women. In humans, a sperm cell with 23 chromosomes will meet an egg cell with 23 chromosomes. This is fertilization. This fertilization will result in an egg cell with 46 chromosomes, that is to say the normal number of chromosomes in a human cell. Half of the chromosomes in the egg cell come from the father and half come from the mother. The production of gametes with 23 chromosomes is done by cell division mechanisms called meiosis, which takes place at the level of the reproductive organs in the germ cells. We will study meiosis in a cell with 4 chromosomes. Chromosome pair 1 is made up of a single red chromosome and a single blue chromosome. Chromosome pair 2 is made up of a single green chromosome and a single brown chromosome. The cell will duplicate its genetic material. Single chromosomes become double chromosomes. The amount of genetic material will double during this stage. During the first division of meiosis, double chromosomes of the same pair will separate and distribute themselves randomly. Here, the double red chromosome with the double green chromosome, and the double blue chromosome with the double brown chromosome. But the random distribution could have been the double blue chromosome with the double green chromosome, and the double brown chromosome with the double red chromosome. During the second division of meiosis, the cell will divide. Each double chromosome separates into two identical single chromosomes, which will then be distributed in the gametes. Meiosis will therefore allow, from a mother cell with 46 chromosomes, to form four gametes with 23 chromosomes. These gametes are not genetically identical . Meiosis, particularly with the random distribution of double chromosomes during the first division, makes it possible to create a great genetic diversity of gametes. [Music] Like a great diversity of sperm to meet a great diversity of eggs. Fertilization is also a process that creates genetic diversity. If we recap, mitosis takes place in somatic cells. It allows, from a mother cell with 46 chromosomes, to give two genetically identical daughter cells with 46 chromosomes. Mitosis allows for the growth, development and cellular renewal of an individual. Meiosis takes place in germ cells. A cell with 46 chromosomes will give rise to four genetically different gametes with 23 chromosomes, thanks to two successive divisions. The video is now finished. I hope you liked it. If you have any questions, don't hesitate to ask me in the comments. We'll see each other very quickly. See you soon. [Music]