Saturday, December 7, 2013

Chromatin

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.
  1.  The DNA and proteins of chromosomes are together called chromatin
  2. Chromatin condenses to form discrete chromosomes as a cell prepares to divide
  3. Chromosome is one DNA molecule and its associated proteins
  4. Appearance changes as cell divides