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NEETZoologyMolecular Basis of Inheritance

When chromatin is viewed under an electron microscope, it shows a 'beads-on-string' appearance. Which of the following statements correctly describes the protein composition and chemical nature of the core of these 'beads'?

Options

  1. AIt is a hexamer of acidic proteins rich in glutamic acid.
  2. BIt is an octamer of acidic proteins rich in valine and leucine.
  3. CIt is an octamer of basic proteins rich in lysine and arginine.
  4. DIt is a tetramer of basic proteins rich in lysine and arginine.

Correct answer

C. It is an octamer of basic proteins rich in lysine and arginine.

Step-by-step solution

The 'beads-on-string' structure seen under an electron microscope represents nucleosomes on the chromatin thread. The core of each nucleosome (the 'bead') is formed by a histone octamer, which consists of eight histone protein molecules. Histones are basic proteins because they are rich in basic amino acid residues, specifically lysine and arginine. Both of these amino acids carry a positive charge in their side chains, which allows the histone octamer to tightly bind the negatively charged DNA. Therefore, the core

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