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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- A. one hydrogen bond
- B. two hydrogen bonds
- C. three hydrogen bonds
- D. a covalent bond
Explanation: Adenine and thymine are held together by two hydrogen bonds, while guanine and cytosine are held by three.
Correct answer: two hydrogen bonds- A. 22%
- B. 28%
- C. 44%
- D. 56%
Explanation: Chargaff's rule applies to the double stranded molecule, so A equals T and G equals C.
Correct answer: 28%- A. they carry identical base sequences
- B. one runs 5' to 3' while the other runs 3' to 5'
- C. they are held together by covalent bonds
- D. they coil in opposite directions around each other
Explanation: Antiparallel refers to the direction of the sugar-phosphate backbones: one strand runs 5' to 3' while its partner runs 3' to 5'.
Correct answer: one runs 5' to 3' while the other runs 3' to 5'- A. Mendel and Morgan
- B. Griffith and Avery
- C. Watson and Crick, using the X ray diffraction data of Rosalind Franklin
- D. Sanger and Gilbert
Explanation: Watson and Crick built the model from Franklin's X ray photographs, which showed the helix and its dimensions, together with Chargaff's…
Correct answer: Watson and Crick, using the X ray diffraction data of Rosalind Franklin- A. Franklin and Wilkins
- B. Watson and Crick
- C. Mendel
- D. Avery
Explanation: Watson and Crick proposed the double helix model in 1953, based on Franklin's X-ray diffraction data.
Correct answer: Watson and Crick- A. Conservative
- B. Semi-conservative
- C. Dispersive
- D. Non-conservative
Explanation: Meselson and Stahl proved DNA replication is semi-conservative: each new DNA has one old and one new strand.
Correct answer: Semi-conservative- A. DNA polymerase
- B. Helicase
- C. Ligase
- D. Primase
Explanation: Helicase breaks hydrogen bonds between base pairs, unwinding the DNA double helix.
Correct answer: Helicase- A. Leading strand
- B. Lagging strand
- C. Both strands equally
- D. Neither strand
Explanation: The lagging strand is synthesized discontinuously as Okazaki fragments because DNA polymerase only works 5'→3'.
Correct answer: Lagging strand- A. Overlapping
- B. Non-overlapping and degenerate
- C. Ambiguous
- D. Different for each organism
Explanation: The genetic code is non-overlapping, degenerate (multiple codons for one amino acid), and universal.
Correct answer: Non-overlapping and degenerate- A. All bacteria
- B. Retroviruses
- C. All eukaryotes
- D. Plants only
Explanation: Reverse transcriptase synthesizes DNA from an RNA template, found in retroviruses like HIV.
Correct answer: Retroviruses- A. Maintains the tertiary structure of enzymes
- B. Provides energy for all cell metabolism
- C. Enables protein to fold properly
- D. Allows DNA act as a genetic blueprint during replication
Explanation: Because adenine always pairs with thymine and guanine with cytosine, each strand specifies the sequence of the other, so separating the…
Correct answer: Allows DNA act as a genetic blueprint during replication- A. Molecular biologists
- B. Microbiologists
- C. Freshwater biologists
- D. Social biologist
Explanation: Molecular biologists study DNA, genes, chromosomes, and mutations at the molecular level to determine how inherited diseases arise.
Correct answer: Molecular biologists- A. Nucleus
- B. Genes
- C. Chromosomes
- D. Nucleolus
Explanation: A gene is a specific segment of DNA that carries information for a functional product, such as a protein or functional RNA, making it the…
Correct answer: Genes- A. Amino acids
- B. RNA
- C. Nucleotides
- D. Polypeptides
Explanation: Nucleic acids carry genetic information and are long chains formed by joining nucleotides, each containing a sugar, phosphate group, and…
Correct answer: Nucleotides- A. A portion of RNA
- B. A linkage group
- C. A portions of DNA
- D. A sequence of Amino
Explanation: A gene is a specific sequence of DNA that contains information for a functional product, such as a protein or functional RNA.
Correct answer: A portions of DNA- A. Histones
- B. Lipoproteins
- C. Polynucleotides
- D. Hydrocarbons
Explanation: Genes are made of polynucleotides because DNA is a polymer consisting of many nucleotide units joined in long chains, and genes are…
Correct answer: Polynucleotides- A. 10A
- B. 20A
- C. 30A
- D. 40A
Explanation: Wilkins's X-ray diffraction data supported a DNA helix diameter of about 20 Å, which is 2 nm because 10 Å = 1 nm and 20 Å ÷ 10 = 2 nm.
Correct answer: 20A- A. Louis Pasture
- B. William Harvey
- C. Charles Darwin
- D. Watson and Crick
Explanation: Watson and Crick proposed the double-helical model of DNA in 1953, using evidence including Chargaff's rules and X-ray diffraction data…
Correct answer: Watson and Crick- A. Appearance of an individual
- B. Genetic basis of few characters
- C. Full set of genes of an individual
- D. All of these
Explanation: A genome is the complete genetic material of an organism, including its full set of genes and associated DNA sequences.
Correct answer: Full set of genes of an individual- A. 5
- B. 10
- C. 20
- D. 25
Explanation: In the common B-form of DNA, one complete turn of the double helix contains about 10 base pairs.
Correct answer: 10Structure of DNA MCQs: common questions
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