Kinétochore

Category: cellular reproduction The kinétochore is an assembly supramoléculaire of Protéine S on the level of the areas centromeric S of the chromosomes mitotic S. It exists two kinétochores by centromère being able at the Mammifère S to interact with 20 to 40 microtubules.

The attachment of the microtubules on the kinétochores is done with the positive part of the microtubules during the prémétaphase and allows the placement of the chromosomes on the equatorial level. It also partly allows the division of the Chromosomes in two identical batches during the Anaphase and with the Métaphase but it is associated with the mechanism of the polar microtubules. One speaks about anaphase has for the mechanisms due to the microtubules kinétochoriens and of anaphase B for the mechanism due to the polar microtubules. The kinétochores play an active role in two forms in the anarchistic movement of the chromosomes allowing their placement on the equatorial center of the plate (or metaphasic).

  • It allows a die Polymérisation activates (surely using ATP) on the level of the positive end of the microtubule involving racourcissement this microtubule. It is known that the Microtubule depolymerizes spontaneously in the intracellular medium but the presence of the kinétochore makes that 80% of depolymerization are done on the level of the positive end.
  • the other mechanism is related to the active transport (ATP) of the chromosomes on the microtubules by Kinésine S and Dynéine S.
The anaphase has, where the chromosomes migrate, utilizes the first mechanism of active depolymerization. It is known that the force of this action is 10000 times superior at the speed of migration of the chromosomes (1µm/min) which one should really have. That is due to another force (called wind astral or polar) which would be opposed to this depolymerization and which would be also used to put the chromosomes on the equatorial level.

External references

cytosquelette and mitosis

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