A chromosome is a DNA molecule with part or all of the genetic material (genome) of an organism. Most eukaryotic chromosomes consist of packaging proteins which, aided through chaperone proteins, bind to and condense the DNA molecule to prevent it from becoming an unmanageable tangle. This 3-dimensional genome shape performs a big position in transcriptional law. Chromosomes are usually visible under a mild microscope only when the cellular is present process the metaphase of cellular division Before this happens, each chromosome is copied once and the copy is joined to the unique by using a centromere, resulting either in an X-shaped shape if the centromere is located within the center of the chromosome or a -arm shape if the centromere is placed near one of the ends. The original chromosome and the replica at the moment are called sister chromatids. During metaphase the X-shape shape is called a metaphase chromosome. In this surprisingly condensed form chromosomes are easiest to distinguish and study. In animal cells, chromosomes attain their highest compaction degree in anaphase in the course of chromosome segregation.