Question

which of the following best describes the components of the dna twisted ladder? (1 point)
the sides are made of alternating polypeptide chains, and the rungs are made of amino acid segments joined by hydrogen bonds.
the sides are made of alternating phosphate - sugar groups, and the rungs are made of complementary nitrogenous bases joined by hydrogen bonds.
the sides are made of alternating nitrogenous bases, and the rungs are made of phosphate - sugar groups joined by hydrogen bonds
the sides are made of alternating amino acids, and the rungs are made of polypeptide chains joined by hydrogen bonds.

Explanation:

DNA has a double - helix structure like a twisted ladder. The sides (backbone) of the DNA ladder are composed of alternating phosphate and sugar (deoxyribose) groups. The rungs of the ladder are made of nitrogenous bases. There are four types of nitrogenous bases: adenine (A), thymine (T), cytosine (C), and guanine (G). Adenine pairs with thymine (A - T) and cytosine pairs with guanine (C - G) through hydrogen bonds.

Answer:

The sides are made of alternating phosphate - sugar groups, and the rungs are made of complementary nitrogenous bases joined by hydrogen bonds.