8.2 Chromosome Structure and Packaging
Within eukaryotic cells, DNA is organized into long linear structures called chromosomes (Figure 4.8). A chromosome is a deoxyribonucleic acid (DNA) molecule with part or all of the genetic material (genome) of an organism. Most eukaryotic chromosomes include packaging proteins which, aided by chaperone proteins, bind to and condense the DNA molecule to prevent it from becoming an unmanageable tangle. Before typical cell division, these chromosomes are duplicated in the process of DNA replication, providing a complete set of chromosomes for each daughter cell. The replicated arms of a chromosome are called chromatids. Before being separated into the daughter cells during mitosis, replicated chromatids are held together by a chromosomal structure called the centromere.
Figure 4.8 Diagram of Replicated and Condensed Eukaryotic Chromosome. (1) Chromatid – one of the two identical parts of the chromosome after S phase. (2) Centromere – the point where the two chromatids are joined together. (3) Short arm is termed p; Long arm is termed q
Image by: Magnus Manske, Dietzel65, and Tryphon