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spindle checkpoint - checkpoint signals

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spindle checkpoint - checkpoint signals

Postby Hudson » Tue Mar 15, 2011 6:33 pm

Hello Biologists!

I'm having trouble with a question. I'm hoping you can offer me some assistance. I'm taking a cell and molecular biology class online and i'm almost done! however, this question is standing in my way!!

Here is the question:

Two types of signals have been implicated in metaphase checkpoint arrest. Consider the results of a recent experiment in which the unattached kinetochore of a monoattached chromosome was destroyed by a laser beam. It was found in this study that, following destruction of the kinetochore, the cell entered anaphase even though this chromosome was not properly aligned at the metaphase plate. How might you interpret this experiment in terms of the checkpoint signals?

Here's what I understand:

Checkpoints are activated through the cell cycle by a series of sensors that recognize DNA damage of cellular abnormalities. If a sensor detects the presence of a defect, it triggers a response that temporarily holds further cell cycle progress so repairs can be made. This is important because undergoing division with genetic damage runs the risk of the cells becoming cancerous. If the DNA is damaged beyond repair, the checkpoint mechanism can transmit a signal that leads to the death of the hazardous cell. The spindle checkpoint operates between metaphase and anaphase. It comes to life when a chromosome fails to align properly at the metaphase plate like in the experiment mentioned above.

For the answer:

It's asking me how i interpret the experiment. So i'm thinking that the checkpoints did their job by destroying the unattached kinetochore because the checkpoints thought that if they didn't destroy the cell, it could be cancerous or lead to aneupoidy and cause defects etc. But what i don't understand is how did the cell cycle continue from metaphase to anaphase without everything properly aligned?
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