Question

The backbone of DNA and RNA is composed of_________ . DNA is double stranded due to interactions between adenine, cytosine, guanine, and thymine, which are_________ . Uracil is a_______ .

Answer 1

The first gap is phosphate sugar skeleton

The second gap is  nitrogenous bases .

The third gap is  nitrogenous base too, found only in RNA.

The skeleton of DNA is the phosphate-sugar succession of which each sugar bears a nitrogenous base.

Nitrogen bases are nitrogenous organic compounds present in nucleic acids in the form of nucleotides in which they are linked to a sugar.

The five main bases are adenine, cytosine, guanine, thymine and uracil.

Answer 2

A sugar-phosphate backbone (alternating grey-dark grey) joins together nucleotides in a DNA sequence. The sugar-phosphate backbone forms the structural framework of nucleic acids, including DNA and RNA. This backbone is composed of alternating sugar and phosphate groups, and defines directionality of the molecule.The two strands run in opposite directions, one going in a 3' to 5' direction and the other going in a 5' to 3' direction. The nitrogenous bases are positioned inside the helix structure like "rungs on a ladder," due to the hydrophobic effect, and stabilized by hydrogen bonding. Uracil is one of the four nucleobases in the nucleic acid of RNA that are represented by the letters A, G, C and U. The others are adenine, cytosine, and guanine. In RNA, uracil binds to adenine via two hydrogen bonds. In DNA, the uracil nucleobase is replaced by thymine. Uracil is a demethylated form of thymine.

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