|MadSci Network: Cell Biology|
The centromere is a DNA sequence on each chromosome on which the kinetochore assembles. The kinetochore then attaches the chromosome to the mitotic spindle apparatus so that the chromosomes can be separated accurately. I have never heard the term "sister centromere" (even though I am a Genetics Prof!), but I suppose you could refer to the centromere regions of two sister chromatids this way. "Chromatids" are replicated chromosomes. Following chromosomal replication (this occurs in S phase - all of the chromosomes are duplicated by DNA replication), the two copies remain attached to each other until anaphase of mitosis. These two attached copies are called "sister chromatids". If you look at a metaphase spread of chromosomes (in which chromosomes look like the "X" shape) you will see the two sister chromatids attached to each other at the centromere (the pinched-in part). Any college level general bio or genetics textbook will show you these concepts and have nice diagrams. I recommend "Biology" by Brooker or "Genetics Analysis and Principles" by Brooker.
Try the links in the MadSci Library for more information on Cell Biology.