DNA structure and how it is packed — NEET & JEE Questions

Question 1 · difficulty L1 · recall

The basic repeating unit of eukaryotic chromatin:

• A. ribosome
• B. operon
• C. centrosome
• D. nucleosome

Question 2 · difficulty L1 · recall

The orientation of the two DNA strands:

• A. covalently crosslinked throughout
• B. antiparallel
• C. randomly oriented
• D. parallel in the same direction

Question 3 · difficulty L2 · understanding

The rule that in double-stranded DNA A equals T and G equals C:

• A. Gause principle
• B. Chargaff rule
• C. Hardy-Weinberg rule
• D. Mendel segregation

Question 4 · difficulty L2 · understanding

What type of bond joins complementary bases across the two DNA strands?

• A. Phosphodiester bonds
• B. Peptide bonds
• C. Hydrogen bonds
• D. Disulfide bonds

Question 5 · difficulty L2 · understanding

In B-DNA, the pitch of the helix is 3.4 nm and there are roughly 10 base pairs per turn. The distance between two consecutive base pairs is therefore approximately

• A. 3.4 nm
• B. 34 nm
• C. 0.34 nm
• D. 1 nm

Question 6 · difficulty L3 · understanding

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

Question 7 · difficulty L3 · understanding

Given below are two statements: Statement I: In prokaryotes, the positively charged DNA is held with some negatively charged proteins in a region called nucleoid. Statement II: In eukaryotes, the negatively charged DNA is wrapped around the positively charged histone octamer to form nucleosome. In the light of the above statements, choose the correct answer from the options given below:

• A. Both Statement I and Statement II are false.
• B. Statement I is correct but Statement II is false.
• C. Statement I is incorrect but Statement II is true.
• D. Both Statement I and Statement II are true.

Question 8 · difficulty L3 · understanding

Read the following statements and choose the set of correct statements: (a) Euchromatin is loosely packed chromatin (b) Heterochromatin is transcriptionally active (c) Histone octamer is wrapped by negatively charged DNA in nucleosome (d) Histones are rich in lysine and arginine (e) A typical nucleosome contains 400 bp of DNA helix Choose the correct answer from the options given below :

• A. (b), (d), (e) only
• B. (a), (c), (d) only
• C. (b), (e) only
• D. (a), (c), (e) only

Question 9 · difficulty L3 · understanding

Which one of the following statements about histones is wrong?

• A. Histones carry positive charge in the side chain
• B. Histones are organized to form a unit of 8 molecules
• C. The pH of histones is slightly acidic
• D. Histones are rich in amino acids - Lysine and Arginine

Question 10 · difficulty L4 · analysis

A DNA segment contains 30% adenine. What percentage of guanine is expected in double-stranded DNA?

• A. 30%
• B. 20%
• C. 40%
• D. 70%