2. short answer: describe the structure of dna, using the term double helix.

Brief Explanations:

DNA has a double - helix structure. It consists of two long polynucleotide chains. The backbone of each chain is made up of alternating deoxyribose sugar and phosphate groups. The nitrogenous bases (adenine, thymine, cytosine, guanine) are attached to the deoxyribose sugars and face inward. Adenine (A) pairs with thymine (T) via two hydrogen bonds, and cytosine (C) pairs with guanine (G) via three hydrogen bonds. These base - paired chains coil around each other to form the double - helix shape, like a twisted ladder where the sugar - phosphate backbones are the sides of the ladder and the base pairs are the rungs.

Answer:

DNA has a double - helix structure. It is composed of two polynucleotide strands. Each strand has a backbone of alternating deoxyribose sugar and phosphate groups. Nitrogenous bases (A, T, C, G) are attached to deoxyribose, with A - T and C - G base - pairing. The two strands coil around each other, forming a twisted - ladder - like double helix, where sugar - phosphate backbones are the ladder sides and base pairs are the rungs.