Mitosis
How is an individual formed?
A new individual is formed after the union of a male gamete (spermatozoon) and a female gamete (oocyte) through fertilization. From this union, it originates a zygote (2n) which, after its development, will constitute an adult individual.
Gamete formation -> Gametogenesis is the formation of gametes or sex cells through meiosis from germ cells.
In this process, germ cells halve the number of cromosomes. Therefore, cells go from having a diploid chromosomal endowment (2n) to having a haploid chromosomal endowment (n).
When is fertilization done?
For fertilization to occur, ovulation must take place. And during this period, there must be sexual intercourse.
Ovulation allows the mature oocyte to detach from the folicle.
Ovulation happens only once in each menstrual cycle and usually occurs 12 to 16 days before the next period.
Fertilization takes place in the Fallopian tubes (the tube that connects the ovary to the uterus).
After this process, the zygot (2n) will begin to develop through a process called mitosis and, at the same time, travel through the Fallopian tube to the uterus. For its parts, the endometrium will prepare for the implantation of the embryo.
Mitosis
Mitosis is a process in which a cell divides into two indentical daughter cells to create cells with the same chromosomal endowment. In other words that is the cells that will form will be diploid (2n).
Mitosis is divided into four phases:
Interphase (previous phase)
The cell's DNA appears dispersed as chromatin and is duplicated in preparation for cell division. This process results in two completely identical sets of chromatin. Outside the nucleus, two replicated centrosomes can see, each containing a pair of centrioles. These structures are main for the process of cell division. During interphase, microtubules extend from these centrosomes.
Prophase
(pro: first, before).
Chromatids condence and form X-shaped structures called chromosomes.
Each chromosome is composed of two sisters chromatids that contain identical genetic information.
At the end of the prophase, the membrane around the nucleus of the cell disappears.
The mitotic spindle, made of microtubules and other proteins, extends through the cell between the centrioles as they move to opposite poles of the cell.
Metaphase
(meta: after, between)
The chromosomes line up perfectly along the center (equator) of the cell.
The centrioles are now at opposite poles of the cell and are attached to each of the chromosomes by the mitotic spindle fiberd that extend from them.
Anaphase
(ana: up, ascending)
The sister chromatids are released from each other by the mitotic spindle that pulls one chromatid to one pole and the other chromatid to the opposite pole.
Telophase
(telos: end)
When the chromatids reach their destination, the mitotic spindle filaments begin to disappear. The chromosomes have become decondensed and become less visible. A membrane forms around each set of chromosomes to create two new nuclei.
Cytokinesis
Cytokinesis is the division of the cell's cytoplasm. It begins at the end of anaphase and is complete during telophase.
At the end of cytokinesis, two genetically identical daugther cells are produced, and these are diploid (2n) cells.
Model About Mitosis
In this way, an individual made up of billions of cells will be formed.