THE FIVE PHASES OF MYTHOSIS

21.04.2021

Formation of the mitotic chromosome formed by two homonymous chromatids joined by the centromere.

Disassembly of the cytoskeleton: assembly of the mitotic spindle. The disappearance of the nuclear envelope and some organelles (RE, AG).

The myotic chromosome: condensation of chromosomes. 30 nm fibers that give rise to supercoiled loops anchored to proteins of the chromosome skeleton. Protein action: topoisomerase 2, condensin, and cohesin: they form the rings that surround the fibers.

Injection of the kinetochore in the centromere. Place where the microtubules are connected. It joins the pericentric heterochromatin with them for separation of the chromatids: cohesin present. Mitotic spindle formation: disassembly of microtubules at the end of the G2 phase (MPAS inactivation) that assemble in prophase. The two pairs of centrioles (Phase S duplication) separate upon entering produce. The centrioles organize the microtubules in the form of "ester" in such a way that when migrating to each pole they contribute to the formation of the bipolar mitotic spindle. Dissociation of the nuclear membrane and disappearance of organelles:

Depolymerization by phosphorylation of the nuclear lamina, makes the nuclear envelope disappear. Poles appear in the nuclear envelope, it enlarges and spreads forming vesicles that disperse, RE and AG disappear. Some organelles remain intact: mitochondria, lysosomes, peroxisomes, and chloroplast.

Prometaphase

Prometaphase is the second phase of mitosis, the process that separates the duplicated genetic material carried in the nucleus of a parent cell into two identical daughter cells. During prometaphase, the physical barrier that encloses the nucleus, called the nuclear envelope, breaks down. The breakdown of the nuclear envelope frees the sister chromatids from the nucleus, which is necessary for separating the nuclear material into two cells. 

Another important event during prometaphase is the development of a protein formation called a kinetochore around the centromere, the central point joining the sister chromatids. Long protein filaments called kinetochore microtubules extend from poles on either end of the cell and attach to the kinetochores. Prometaphase is followed by the third phase of mitosis, known as metaphase. 

Anaphasis

Chromosomes are a partner on the back: spheronization. Chromatids move to opposite poles of use: anaphase A to spindle poles even more: directions or states due to polymerization/elongation of microtubules: anaphase B How do you separate the chromatids?

Proteolysis

Metaphase-Anaphase regulation point: activation of an anaphase promoter complex (APC) Degradation of an anaphase inhibitor by the proteasome: the destruction of the securva release from cohesin-breaking separation. Cyclin degradation: G1 phase.

How do you separate the poles of the spindle even further? As before, the dynamics of the microtubules in the anaphase by shortening of the microtubules (flow of units through the microtubules: chromatic movement) Anaphase A + elongation of the polar (addition of tubulin).

Telophase 

The chromosomes are grouped at the poles. Disperse (decondensation: 30nm dibs) Assembly of the nuclear envelope: dephosphorylation in n lamellae. Dorman the ER and the AG. Daughter cell formation. The decrease in M ​​cyclins would cause the daughter cells to enter the G1 phase of the interface.