Question

1. Describe the parts of the nucleotide, including the difference between ribose and deoxyribose, the difference between the different bases, purines vs pyrimidines.
2. Describe the basic structure of DNA (deoxyribonucleic acid), including complementary base pairing, antiparallel strands, 5’ vs 3’, and double helical shape.
3. Utilize the following terms to describe the structure of DNA and process and products of replication: nucleotide, adenine, guanine, cytosine, thymine, purine, pyrimidine, sugar-phosphate backbone, hydrogen bonds, anti-parallel, semi-conservative, topoisomerase.
4. Explain DNA replication, including all the enzymes involved.

Answer 1

DNA is deoxyribonucleic acid. It is the genetic material present in all the living organisms. It is a polymer of nucleotides.

Nucleotides are composed of three molecules, A nitrogenous base, a deoxyribose sugar and a phosphate group.

Nitrogenous base attaches to deoxyribose sugar by N, 1 glycosidic linkage. This leads to the formation of a nucleoside.

Phosphate group attaches to deoxyribose sugar by forming 3' 5' phosphodiester bond.

Nitrogenous base are of two types, purine and pyrimidine. Purines are heterocyclic compounds and include adenine and guanine. Pyrimidine are cyclic compounds and include thymine and cytosine.

Deoxyribose is a pentose sugar because it contains 5 carbons. Deoxyribose is different from ribose in the absence of hydroxyl group at 2' position.

Phosphate group is negatively charged group which imparts an overall negative charge to DNA.

The DNA is double helical in all eukaryotes and prokaryotes. The backbone of the double helix is made up of sugar phosphate and make the 2 strands of the double helix. The nitrogenous bases are held in between the two strands like stacks of ladder.

The two strands run in anti parallel direction, one in 5' to 3' and the other in 3' to 5' direction.

The two strands are held together with each other by complementary base pairing between nitrogenous bases. Adenine pairs with thymine by two hydrogen bonds and guanine pairs with cytosine by 3 hydrogen bonds.

One turn of DNA consists of one major groove and one minor groove. In between 1 turn, there are 10 nitrogenous base pairs. The diameter of the double helix is 2 nm. The pitch, that is the length of One Turn which includes one major groove and one minor groove is 3.4 nm.

This is an answer to first two questions.

Please rate.