Chemical composition of chromatin, Biology

CHEMICAL COMPOSITION OF CHROMATIN

  1. Chromatin threads composed of DNA (31 %), RNA (2-5%) and proteins (Histon-36%, Non histon 28%).
  2. Histone and protamines are basic proteins. Histone protein composed of mainly Arginine, lysine and Histidine amino acids. Protamine has more arginine but lysine is absent. Histone occupy the major grooves of DNA at an angle of 30° to the helix, and it neutralise negative charges of intemucleotide phosphate in DNA. In procaryotes polyamines have simillar functions.
  3. Histone protein discovered by Kossel. (Kossel also discovered purines and pyrimidines). On the basis of relative amount of arginine and lysine there are five types of histone proteins i.e. H2A, H2B, H3, H4 and H1.H3 and H4 are arginine rich, H2A and H2B are slightly lysine rich and H1 is highly lysine rich.
  4. Non Histone protein of chromatin mainly composed of Tryptophan and Tyrosine amino acids. Non histone proteins occur more in euchromatin part where these activate segments of DNA for transcription.
  5. Klug worked out ultrastructure of chromatin. Under electron microscope chromatin appears beaded. Beads are called Nucleosome or Nu-body by Wood cock and P. oudet (1975) .Nucleosomes are 11 nm in diameter and 5.7 nm in height. Nucleosome model of chromatin proposed by R. Kornberg. Each nucleosome composed of 140 pairs of nucleotides and 8 histone molecules.
  6. Central core of nucleosome composed of histon and nucleotides of DNA form two coils (1% ) around this octamer of histone (two molecules each of H2A, H2B, H3, H4). Nucleosomes are linked in a string by thin threads called linker. Linker composed of 60 pairs of nucleotides and one histone molecule (H1),
  7. In chromatin, nucleosomes form coils called Solenoid of 30 nm in diameter. Each solenoid composed of six nucleosomes.
Posted Date: 10/5/2012 8:03:56 AM | Location : United States







Related Discussions:- Chemical composition of chromatin, Assignment Help, Ask Question on Chemical composition of chromatin, Get Answer, Expert's Help, Chemical composition of chromatin Discussions

Write discussion on Chemical composition of chromatin
Your posts are moderated
Related Questions
What are plankton, nekton and benthos? Plankton, nekton and benthos are the three groups into which aquatic living beings may be separated. The plankton is formed by the alg

Q. Can Obesity causes the cardiovascular disease? Obesity is established as a leading predictor of CAD and is associated with several cardiovascular risk factors like cholester

M yc ot o xi c osi s There are several types of mycotoxins (toxins produced by the fungi) e.g. aflatoxin, ochratoxin etc. Many species of fungi produce them but Aspergi

Define Information Required for Management of Emergencies? Management or intervention needs accurate information about the actual situation and includes many non-nutritional co



- The chromosomes at each pole uncoil and elongate to form the chromatin. - A nucleolus reappears at each pole. - Spindle fibers and asters disappear and centrioles split. - A nu

Burrowing - Mechanics of Locomotion Some polychaetes are burrowing. Instance is glycerides and capitellidae. Their parapodia are smaller. Burrowing is done by protrusion of pr


is a wheat plant a eustele or a siphonostele or a protostele?