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Free Structure of DNA MCQs with Answers

69 Structure of DNA MCQs from Biology, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.

DNA structure includes nucleotides made of deoxyribose, phosphate and nitrogenous bases, arranged in two antiparallel polynucleotide strands. Questions cover the double helix, phosphodiester and hydrogen bonds, complementary base pairing between adenine and thymine and between guanine and cytosine, and the significance of major and minor grooves.

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69 questions · page 4 of 4

61. The two chains of DNA occur side by side in a:

  • A. Straight direction
  • B. Parallel but straight
  • C. Antiparallel and straight
  • D. Antiparallel and spirally twisted

Explanation: DNA is a double helix formed by two strands of nucleotides. These strands run in opposite directions (antiparallel) and are twisted around…

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Correct answer: Antiparallel and spirally twisted

62. In Eukaryotes, DNA replication proceeds at the rate of:

  • A. 50 base pairs per second
  • B. 40 base pairs per second
  • C. 20 base pairs per second
  • D. 30 base pairs per second

Explanation: Eukaryotic DNA replication typically occurs at a rate of approximately 50 base pairs per second.

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Correct answer: 50 base pairs per second

63. The genome of the most animals and higher plants is:

  • A. DNA
  • B. RNA
  • C. Both DNA and RNA
  • D. Either DNA or RNA

Explanation: Plant genome assembly represents the complete genomic sequence of a plant species, which is assembled into chromosomes and other…

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Correct answer: DNA

64. Replication of DNA occurs during:

  • A. Interphase
  • B. Prophase
  • C. Metaphase
  • D. Anaphase

Explanation: DNA replication occurs during S-stage of interphase.

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Correct answer: Interphase

65. Phosphodiester linkage is formed between.

  • A. Two nucleotide bases
  • B. Amino acid
  • C. Two sugar
  • D. Nucleotides and phosphates

Explanation: In the polynucleotide, adjacent nucleotides are joined by a phosphodiester linkage, which consists of a phosphate group that links the…

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Correct answer: Nucleotides and phosphates

66. The number of hydrogen bonds between guanine and cytosine are:

  • A. One
  • B. Two
  • C. Three
  • D. Four

Explanation: The Adenine - Thymine base pair is held together by 2 hydrogen bonds while the Guanine - Cytosine base pair is held together by 3 hydrogen…

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Correct answer: Three

67. Individuality of every persons is maintained by nucleotide genome sequence difference of:

  • A. 0.1%
  • B. 2%
  • C. 3%
  • D. 5%

Explanation: Human beings share 99.9% of their genome sequence, making 0.1% the portion that accounts for individual genetic differences.

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Correct answer: 0.1%

68. Which one among the following is double ring structure?

  • A. Cytosine
  • B. Thymine
  • C. Guanine
  • D. Uracil

Explanation: Cytosine, thymine, and guanine are nitrogenous bases found in DNA and RNA.

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Correct answer: Guanine

69. Purines are _ nitrogenous bases.

  • A. Double ringed
  • B. Single ringed
  • C. Double bond
  • D. Single bond

Explanation: Purines are a type of nitrogenous base found in DNA and RNA, characterized by a double-ring structure.

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Correct answer: Double ringed
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