DNA Structure Multiple Choice Questions and Answers

1 In a DNA double helix the bases are held together by hydrogen bonds. These hydrogen bonds are _________

A Ionic bonds

B Covalent bonds

C Non-covalent bonds

D Van der Waals forces

Answer: Non-covalent bonds

2 With respect to the importance of hydrogen bonding and DNA double helix stability, which of the following statements is false?

A Decreases the entropy

B Contributes to the thermodynamic stability

C Favorable tautomeric form of nucleotide bases

D Specificity of base pairing

View Answer

Answer: Decreases the entropy

3 Levene investigated and found that the nucleic acid is composed of poly-nucleotides and each nucleotide is composed of one base, a sugar molecule and a phosphate. This was performed on the genome of________________

A Yeast

B Bacteria

C Fungi

D WBCs

View Answer

Answer: Yeast

4 A nucleoside is composed of

A a base+ a sugar+ phosphate

B a base+ a phosphate

C a base+ a sugar

D none of these

View Answer

Answer: a base+ a sugar

5 DNA is the genetic material in

A prokaryote and eukaryote

B viruses, prokaryote and eukaryote

C in some viruses, prokaryotes and eukaryotes

D only in eukaryotes

View Answer

Answer: in some viruses, prokaryotes and eukaryotes

6 Chromatin is composed of

A Proteins Only

B Nucleic Acids Only

C Nucleic Acids And Protein

D None Of These

View Answer

Answer: Nucleic Acids And Protein

7 Adjacent nucleotides are joined by

A Phosphodiester Bond

B Covalent Bond

C Ionic Bond

D none of the above

View Answer

Answer: Phosphodiester Bond

8 The type of sugar in DNA are

A Hexose

B Pentose

C Tetrose

D Triose

View Answer

Answer: Pentose

9 The length of DNA having 23 base pairs is

A 74.8 Ao

B 78 Ao

C 78.4 Ao

D 78.2 Ao

View Answer

Answer: 74.8 Ao

10 Which of the following statements is incorrect about t RNA species?

A All t RNAs have between 10-20 nucleotides

B They make up 15% of the t RNA in the cell

C They have the smallest size of the three major species

D There is at least one specific t RNA molecule for each of the 20 amino acids

View Answer

Answer: All t RNAs have between 10-20 nucleotides

11 When the B DNA is slightly dehydrated in the laboratory it takes on-

A A conformation

B Negative supercoils

C Positive supercoils

D Z conformation

View Answer

Answer: A conformation

12 Which of the following nucleic acids has a left-handed helix?

A A-DNA

B B DNA

C m-RNA

D Z-DNA

View Answer

Answer: Z-DNA

13 Which of the following processes would not lead to disruption of the nucleosomal structure?

A Carboxylation

B Acetylation

C Methylation

D None Of The Above

View Answer

Answer: Methylation

14 Choose the incorrect statement about histones

A H2A and H2B form dimers

B H3 and H4 form a tetramer

C H2A, H2B, H3, and H4 form the core of a nucleosome

D H1 histones are tightly bound to chromatin

View Answer

Answer: H1 histones are tightly bound to chromatin

15 Which of the following has the highest percentage of modified bases ?

A t-RNA

B hn RNA

C sn RNA

D m-RNA

View Answer

Answer: t-RNA

16 Choose the incorrect statement about an RNA:

A Has a single stranded structure

B Instead of Uracil contains the ribonucleotides of thymine

C Does not obey Chargaff’s rule

D Does not exhibit Watson and crick’s base pairing

View Answer

Answer: Instead of Uracil contains the ribonucleotides of thymine

17 An endonuclease is an enzyme that hydrolyzes:

A A phosphodiester bond located in the interior of a polynucleotide

B A nucleotide from only the 3’ end of an oligonucleotide

C A nucleotide from either terminal of an oligonucleotide

D A bond only in the specific sequence of nucleotides

View Answer

Answer: A phosphodiester bond located in the interior of a polynucleotide

18 Which of the following RNAs contains both a 7-Methyl guanosine triphosphate cap and polyadenylate segment?

A m-RNA

B hn RNA

C t-RNA

D None of the above

View Answer

Answer: m-RNA

19 The first X-ray diffraction patterns of DNA were taken in 1938 by ___________

A Rosalind Franklin

B Francis H. Crick

C William Asbury

D none of the above

View Answer

Answer: William Asbury

20 In early 1950s high quality X-ray diffraction photographs of DNA suggesting the DNA being double helix and composed of two nucleotide strands. Who took those photographs?

A Rosalind Franklin and Maurice Wilkins

B Rosalind Franklin

C William Asbury

D Francis H. Crick and James D. Watson

View Answer