MadSci Network: Cell Biology

Re: How is the DNA in protozoa separated during cell division?

Date: Thu Sep 23 20:18:02 1999
Posted By: Dean Jacobson, Faculty Biology, Whitworth College
Area of science: Cell Biology
ID: 935694888.Cb

You are right: being typical eukaryotes, they all have a process of mitosis.
There are some neat minor variations among certain protists from the 
standard mitosis of the multi-cellular eukaryotes (actually, fungi also have 
a weird variation of mitosis...).   For example,  dinoflagellates never 
destroy their nuclear envelope during mitosis (they also have strange 
sausage shaped chromosomes, sometimes as many as 200 of them, which never 
"decondense"; even in interphase you can see these chromosomes inside the 
nucleus with an ordinary microscope.)  This is how dinoflagellate mitosis 
happens:  cytoplasmic "tunnels" which contain cytoplasmic microtubules 
burrow through the nucleus from one side to the other, and the chromosomes 
attach to the inner surface of the nuclear envelope surrounding these 
parallel tunnels.  Then, the microtubules pull the chromosomes to opposite 
sides of the nucleus, which pinches in half.  Weird, but the result of this 
"closed" mitosis is the same as typical "open" mitosis found in plant and 
animals cells.

Cheers, and sorry for the wait,
Dean Jacobson, dinoflagellate naturalist

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