Chromatin is composed of long molecules of DNA, along with proteins. Most of the time, the chromatin is arranged as a long, tangled mass of threads in the nucleus. However, during cell division, the chromatin becomes tightly coiled into short, dense structures called chromosomes (chromo=color; some=body). Chromatin and chromosomes are really the same molecules, but they differ in structural arrangement. In addition to chromosomes, the nucleus may also contain one, two, or several nucleoli. A nucleolus is the site of ribosome manufacture. Specific parts of the DNA become organized within the nucleus to produce ribosomes. A nucleolus is composed of this DNA, specific granules, and partially completed ribosomes.
- The DNA and proteins of chromosomes are together called chromatin
- Chromatin condenses to form discrete chromosomes as a cell prepares to divide
- Chromosome is one DNA molecule and its associated proteins
- Appearance changes as cell divides