Friday, January 9, 2009

And More TQTQ 1-8-09 Responses

Zena asked - What is meristem? Meristem is a type of cell in plants that has not differentiated. This means that the cells have not become a specific type of cell. Because of this they can become many types of cell. So when you see that we are looking at apical meristem in the onion root tip this tells us that the tissue is likely rapidly dividing and can become vascular tissue, epidermis, root hairs, root cap, and others.

Zena also asked - Does an ameoba have cell division? Yes, they do what is called binary fission. During this process the nucleus does replicate its DNA and divides it equally. This is how you get more ameobas.

Wendy asked - Is it a conicidence that the cell cycle and one day are 24 hours in duration? The answer for the cells we were looking at, yes. Remember, there is a great range of cell cycle times. For example a nerve cell never divides, whereas a bacterial cell can divide in as few as 15 minutes. So the time for cell cycle completion depends on the type of cell you are looking at.

Going to the lab now, more later.

Mr. Baker


Shauna said...

Under what conditions would a cell stop dividing?

Mr. Baker said...


As you know, cell division is regulated by the levels of CDK. However, it is growth factors in the fluid surrounding cells that signal cells to proliferate (grow and divide). Interestingly, most cells in the human body are in G-zero stage but can be induced to leave G-zero and divide. Some cells like nerve cells are fixed in G-zero and this seems to be due to control switches that were set when the cell differentiated.

Shauna said...

Oh so they are stuck in G0 until their switch is turned on?

Mr. Baker said...

You got it.