DNA Structure Objective Type Questions and Answers

21 In 1952, an unambiguous established work in the laboratory of Alexander Todd led to the discovery of _____________

A 3’-5’ phosphodiester linkage regularly links the nucleotides of DNA

B Chemical nature of DNA

C Nucleic acid strands are held together by hydrogen bonds

D X-ray diffraction structure of DNA

Answer: 3’-5’ phosphodiester linkage regularly links the nucleotides of DNA

22 In the late 1970s non double helical form of DNA was also suggested but was discarded on the basis of certain factors. Which of the following is not a factor responsible?

A Nuclein

B Nucleosome core particle

C Topoisomerase

D X-ray crystallography

View Answer

Answer: Nuclein

23 Genetic mutation occurs in

A DNA

B Protein

C RNA

D Nucleus

View Answer

Answer: DNA

24 DNA is present in

A nucleus, mitochondria and choloroplast

B nucleus only

C nucleus, mitochondria and ER

D nucleus, mitochondria and RER

View Answer

Answer: nucleus, mitochondria and choloroplast

25 The two strands in a DNA double is joined by

A Hydrogen bond

B Co-valent bond

C phosphodiester bond

D ionic bond

View Answer

Answer: Hydrogen bond

26 The basic repeating units of a DNA molecule is

A Nucleotide

B Nucleoside

C Histones

D None Of These

View Answer

Answer: Nucleotide

27 Left handed DNA

A Z-DNA

B A-DNA

C B-DNA

D none of the above

View Answer

Answer: Z-DNA

28 The monomeric deoxyribonucleotide units of DNA include all except-

A Deoxyuridylate

B Deoxyadenylate

C Deoxycytidylate

D Deoxyguanylate

View Answer

Answer: Deoxyuridylate

29 Chargaff’s rule states that in a double stranded DNA molecule-

A Concentration of Deoxyadenosine (A) nucleotides equals that of Deoxy guanosine (G) nucleotides

B Concentration of Deoxy cytidine (C) nucleotides equals that of Thymidine (T) nucleotides

C Concentration of Deoxyadenosine (A) nucleotides equals that of Thymidine (T) nucleotides

D All of the above

View Answer

Answer: Concentration of Deoxyadenosine (A) nucleotides equals that of Thymidine (T) nucleotides

30 The Z DNA helix:

A Tends to be found at the 3’ end of genes

B Has fewer base pairs per turn than the B DNA

C Is inhibited by methylation of the bases

D Has alternating GC sequences

View Answer

Answer: Has alternating GC sequences

31 Which of the following types of RNA participate in RNA processing?

A Small nuclear RNA (snRNA)

B Heterogeneous nuclear RNA (hnRNA)

C Small Interfering RNAs (siRNAs)

D r-RNA

View Answer

Answer: Small nuclear RNA (snRNA)

32 The Small Nuclear RNAs (snRNAs) are rich in-

A Adenine

B Cytosine

C Thymine

D Uracil

View Answer

Answer: Uracil

33 Z-DNA have a

A Double helical nature

B single stranded nature

C Zig-Zag apperarance

D None Of The Above

View Answer

Answer: Zig-Zag apperarance

34 A short length of DNA molecule has 80 thymine and 80 guanine bases. The total number of nucleotide in the DNA fragment is

A 320

B 57

C 640

D None

View Answer

Answer: 320

35 Choose the incorrect statement out of the following:

A Single turn of B-DNA about the axis of the molecule contains six base pairs

B Double-stranded DNA exists in at least six forms (A–E and Z)

C The distance spanned by one turn of B-DNA is 3.4 nm

D The B form is usually found under physiologic conditions

View Answer

Answer: Single turn of B-DNA about the axis of the molecule contains six base pairs

36 When the DNA molecule is twisted in the direction opposite from the clockwise turns of the right-handed double helix found in B-DNA, such DNA is said to have acquired-

A Positive supercoils

B Negative supercoils

C Z form

D A form

View Answer