Re: What is the centromere and what is its function?

I am not sure how much you know about Cell division.  The genetic material 
in a non dividing cell, is contained present in the nucleus as a network 
of filaments called the Chromonemata.  As soon as Cell division begins, 
the Chromonmata network condenses to form rod like structures called 
Chromosomes.  Each Chromosome is made up of a pair of Chromatids and there 
is point at which these Chromatids join called the Centromere.

The Centromere contains a structure called the Kinetochore.  The 
Kinetochore functions as an attachment site for spindle fibres-  These 
Spindle Fibres will then pull the Chromatids to opposite ends of the cell 
before the cell divides.  Thus clearly the Centromere and the Kinetochore 
have an important role to play in Chromosome segregation during cell 
division.  What I have outlined above is what is referred to as Mitosis.  
The Centromere and the Kinetochore also have an important part to play in 
the segragation of Chromosomes during Meiosis, the process of Gamete 
formation. 

 
If you were to look at a Chromosome down the microscope, you would see the 
Centromere as an indentation in the structure of the Chromosome.  This 
indentation is always located in the same position in different types of 
Chromosomes making it a useful feature for identifying Chromosomes in 
Cytogenetics labs.

You can find out more information on the Centromere as well as Mitosis and 
Meiosis on the Britannica Web Site on http://search.britannica.com/search?
query=Chromosome or alternatively if you look at Molecular Biology of the 
Cell (Albert et al) you will find further information