# Chromatid **Chromatids** are the little worm-like segments of a replicated [[chromosome]]. They are *not* used to describe the structure of an unreplicated chromosome, and are often referred to as a pair of "sister chromatids" Although they may look like two separate chromosomes, they are in fact, a single chromosome. ![[homologous pair.png]] An analogy: If you made a photocopy of a page in a book, you have two pages, but no new information. For the sake of illustration, you can imagine the two pages are stapled together. ## Centromere and Kinetochore The **centromere** is the part in the middle of the X shape that holds the sister chromatids together. The **kinetochore** is a structure on the chromasome that the [[microtubules]] attach to pull the sister chromatids apart during [[cell division]]. ## Not to be Confused With: Homologous Pairs Sister chromatids are two halves of a single replicated chromosomes, and a [[homologous pair|homologous pairs]] describe two different chromosomes with the same genes. ___