Question

the table lists some characteristics of a dna double helix structure that a student wrote in an assessment. which listed characteristics of dna are true? 1. the purine bases always pair with the pyrimidine bases. 2. the nitrogenous bases are attached to the sugar of the dna molecule. 3. the two strands of the dna double helix are held together by phosphate bonds. 4. the sugar molecules on the two strands of the dna helix are linked to each other by hydrogen bonds. o 1 and 2 o 2 and 3 o 3 and 4 o 4 and 1

Explanation:

1. In DNA, purine - pyrimidine base - pairing (A - T, G - C) is a fundamental rule.
2. Nitrogenous bases are attached to the sugar in the DNA molecule's backbone.
3. The two strands of DNA are held together by hydrogen bonds, not phosphate bonds.
4. Sugar - phosphate backbones are linked by phosphodiester bonds, not hydrogen bonds between sugars.

Answer:

A. 1 and 2