Centromeres

Eukaryotic chromosomes also have a specialized structure called the centromere. This is the location at which the spindle is joined during cell division allowing for the segregation of homologs or sister chromatid. Below is shown the consensus sequence of the centromere region from yeast which is quite short and contains some conserved nucleotide sequences (called CEN in yeast) that apparently help to define it as a centromere. Yeast, though, is a bit unusual: most eukaryotes have much longer centromere regions, around 40kb in length, than what is found in yeast and contains a lot of repetitive sequences. As noted above, we also find that in many eukaryotes nucleosomes in the centromere region contain an H3 variant called CENP-A.