[Campbell Biology P.134] Which of the following statements accurately describes the structur... | Practice Question

Which of the following statements accurately describes the structure and directionality of a polynucleotide, as depicted and described in the text?

  • A: The nitrogenous bases form the repeating pattern of the sugar-phosphate backbone.
  • B: A polynucleotide has directionality from its 3' end, which has a phosphate group, to its 5' end, which has a hydroxyl group.
  • C: Adjacent nucleotides in a polynucleotide are joined by phosphodiester linkages, forming a sugar-phosphate backbone.
  • D: The 5' end of a polynucleotide terminates with a hydroxyl group, while the 3' end terminates with a phosphate group.

Explanation

The text explains: "The linkage of nucleotides into a polynucleotide involves a condensation reaction... adjacent nucleotides are joined by a phosphodiester linkage, which consists of a phosphate group that covalently links the sugars of two nucleotides. This bonding results in a repeating pattern of sugar-phosphate units called the sugar-phosphate backbone." This directly supports option C. The text also clarifies that bases are not part of the backbone and that the 5' end has a phosphate while the 3' end has a hydroxyl group.