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Imagine that you are a wizard with an elaborate collection of microneedles. After drawing a ritual circle around your microscope, lighting incense, and speaking an incantation, you are able to stab a single unaligned chromosome and apply tension across its kinetochores. When you do so, the cells progress into anaphase. You decide to repeat your spellcasting with cells that lack cdc20. Do these cells progress into anaphase

Sagot :

marianaegarciaperedo

Answer:

No. If cells lack cdc20, they can not progress into anaphase.

Explanation:

Many regulator molecules act during the different stages of the mitosis process to make it possible.

You need to know that there are too many factors interacting with each other, activating and deactivating to pass from one stage to another. Here, we are mentioning only a few of them, with the principal goal of answering the question.

  • Cyclins are proteins that regulate the whole cell cycle. There are different types of cycling, each of them acting on a different stage. When the cell is going through one of the stages, the only cyclin in high levels is the one that is regulating that phase. Once that stage is over, that cyclin concentration decreases, and the following one increases. For instance, cyclin M regulates the metaphase, and when the cell is going to the anaphase, cyclin M decreases while cyclin A increases.
  • Cohesin proteins keep sister chromatids together during cellular division. In metaphase, sister chromatids are held together until they reach the Anaphase, during which another enzyme activates to break the bonds and separate the chromatids. This protein is the separase. During metaphase, separase is inhibited by securin, which is another protein. But when the cell is going in anaphase, separase activates to break the bonds.  
  • The anaphase-promoting complex/cyclosome, APC/C, controls the progression of mitosis. It is inactive until the cell reaches the metaphase stage. During metaphase, APC/C joins the substrate Cdc20 and together regulate the transition from metaphase to anaphase.

The complex regulates the presence of cyclin M at the final stages of metaphase to allow cyclin A to increase. It also degrades inhibitors such as securin. Through this action, it activates separase, letting the sister chromatids separate during anaphase.

So the complex APC/C-Cdc20 controls the transition metaphase-anaphase. It promotes anaphase and activates separase by degrading Cyclin M and securin.

Some studies about the complex APC/C-Cdc20 have proven that whenever Cdc20 is lacking or blocked, cyclin M and securin accumulate, and the cell can not go from metaphase to anaphase and the mitosis process stops. Researchers concluded that Cdc20 is essential for the transition from one stage to the other.

When Cdc20 is lacking, APC/C can not activate to accomplish functions such as degrading Cyclin M and securin.

  • If cyclin M remains present, the cell can not go to the anaphase.
  • If securin remains present, separase remains inhibited and chromatid sisters can not separate.  
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