LIFE SCIENCE

Detailed explanation-1: -The nucleotides are covalently linked together in a chain through the sugars and phosphates, which thus form a “backbone” of alternating sugar-phosphate-sugar-phosphate (see Figure 4-3).

Detailed explanation-2: -DNA stands for “deoxyribonucleic acid.” The backbone of DNA is comprised of alternating sugar and phosphate units, in which the sugar is deoxyribose.

Detailed explanation-3: -DNA is composed of repeating units called nucelotides or nucleotide bases.

Detailed explanation-4: -Nucleotides are made up of the following: sugar + phosphate + nitrogenous base. In a DNA double helix, the nitrogenous bases are located on the inside, while the sugar and phosphate groups are on the outside, forming the “backbone” of the DNA double helix.