Question

Which of the following statements are correct with reference to packaging of DNA helix?
A. Histones are organized to form a unit of eight molecules called histone octamer.
B. Histones are negatively charged basic proteins.
C. Histones are rich in the basic amino acid residues – lysine and arginine.
D. The positively charged DNA is wrapped around the histone octamer to form nucleosome.
E. The packaging of chromatin at higher levels requires an additional set of proteins called non-histone chromosomal proteins. Choose the correct answer from the options given below :

• A. A, B and D only
• B. B, D and E only
• C. A, C and E only
• D. C, D and E only

Hint:

Remember: DNA is Decidedly Negative (due to phosphate groups). Histones are Highly positive basic proteins. Opposites attract to form the nucleosome!

Answer 1

The Correct Option is C

Step 1: Understanding the Question
The question asks to evaluate several statements concerning the organization of DNA within the eukaryotic nucleus. Because DNA is very long, it must be tightly wrapped and packaged using specialized proteins called histones and non-histone chromosomal proteins. Step 2: Key Formula or Approach
Recall the chemistry of DNA and Histones:
- DNA is an acid (Deoxyribonucleic acid), so it is negatively charged.
- Histones are basic proteins, so they are positively charged.
- Opposites attract, allowing DNA to wrap around histones.
Step 3: Detailed Explanation
Statement A: Eight histone molecules (2 each of H2A, H2B, H3, H4) come together to form an "octamer." This is correct.
Statement B: Histones are positively charged, not negative. This is incorrect.
Statement C: The positive charge of histones comes from the high presence of basic amino acids: Lysine and Arginine. This is correct.
Statement D: DNA is negatively charged, not positive. This is incorrect.
Statement E: While histones handle the basic "beads-on-a-string" level, further folding into complex chromosomes requires Non-Histone Chromosomal (NHC) proteins. This is correct.
Step 4: Final Answer
Statements A, C, and E are the only correct facts. Therefore, (A) is the correct choice.