The two strands of a DNA double helix are described as antiparallel, which means that
Correct answer: B. one runs 5' to 3' while the other runs 3' to 5'
- 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'. This is why replication is continuous on the leading strand and discontinuous, in Okazaki fragments, on the lagging strand. The strands are complementary rather than identical, and they are held together by hydrogen bonds.
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About Structure of DNA
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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