# DBT JRF 2020 — Question 13

Exam: DBT JRF 2020 · Section: A · Topic: Biochemistry · Difficulty: Easy

## Question

Histones

## Options

- **A.** are negatively-charged globular proteins
- **B.** contain high amount of basic amino acids
- **C.** have molecular weights in excess of 100,000 Da
- **D.** contain both $\alpha$ -helix and $\beta$ -pleated sheet

## Answer

Option B

## Explanation

Histones are small, positively charged (basic) nuclear proteins that package DNA into nucleosomes. They are rich in the basic amino acids lysine (Lys, K) and arginine (Arg, R), which carry positive charges at physiological pH. These positive charges allow electrostatic interaction with the negatively charged phosphate backbone of DNA. Histones are NOT negatively charged (ruling out option 1), their molecular weights are small (~11–21 kDa, not >100,000 Da), and while they do contain α-helical regions, the question points to the most defining characteristic — high basic amino acid content.

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