LIFE SCIENCE

Detailed explanation-1: -DNA consists of two strands that wind around each other like a twisted ladder. Each strand has a backbone made of alternating sugar (deoxyribose) and phosphate groups. Attached to each sugar is one of four bases–adenine (A), cytosine (C), guanine (G), or thymine (T).

Detailed explanation-2: -A free, unincorporated nucleotide usually exists in a triphosphate form; that is, it contains a chain of three phosphates. In DNA, however, it loses two of these phosphate groups, so that only one phosphate is incorporated into a strand of DNA.

Detailed explanation-3: -These bonds are called phosphodiester bonds, and the sugar-phosphate backbone is described as extending, or growing, in the 5’ to 3’ direction when the molecule is synthesized.

Detailed explanation-4: -A phosphate backbone is the fixed, structural feature from which nucleic acids protrude in DNA and RNA. This is formed by the repeating sequence of a phosphate group and deoxyribose, connected in sequence by phosphodiester bonds.

Detailed explanation-5: -The DNA strand’s “backbone” is constituted by pentose sugar and phosphate, while the nitrogenous bases project inside forming the bridges between the strands.