Question

molecular structure of DNA​

Answer 1

Answer:

DNA structure

DNA is made up of molecules called nucleotides. Each nucleotide contains a phosphate group, a sugar group and a nitrogen base. The four types of nitrogen bases are adenine (A), thymine (T), guanine (G) and cytosine (C).

Answer 2

Explanation:

I Primary structure of the molecule: covalent backbone and bases aside

I-1 Phosphoric acid

I-2 Sugar

I-3 Nitrogenous bases

II Secondary and tertiary structures of the molecule -Three-dimentional conformation of DNA

II.1 Dinucleotides

II.2 DNA molecule

II.2.1 Hydrogen bonds: bases pairing

II.2.2 Major groove and minor groove

II.3 Non-B DNA

II.3.1 Z-DNA

II.3.2 Cruciform DNA and hairpin DNA

II.3.3 H-DNA or triplex DNA

II.3.4 G4-DNA

III Quaternary structure of the molecule - Chromatin

IV Various

IV.1 DNA and mitochondria

IV.2 DNA denaturation

Explain-

Deoxyribonucleic acid (DNA) IS the genetic information of most living organisms (a contrario, some viruses, called retroviruses, use ribonucleic acid as genetic information).

- DNA can be copied over generations of cells: DNA replication

- DNA can be translated into proteins: DNA transcription into RNA, further translated into proteins ,

- DNA can be repaired when needed: DNA repair .

Ribonucleic acids (RNAs) are described in another chapter ( mRNA, r-RNA, t-RNA... )

- DNA is a polymere, made of units called nucleotides (or mononucleotides).

- Nucleotides also have other functions: (energy carriers: ATP, GTP; cellular respiration: NAD, FAD; signal transduction: cyclic AMP; coenzymes: CoA, UDP; vitamins: nicotinamide mononucleotide, Vit B2).

Using the protein nomenclature, we could speak in terms of primary, secondary, tertiary and quaternary structures of the molecule:

I Primary structure of the molecule: covalent backbone and bases aside

A nucleoside is made of a sugar + a nitrogenous base.

A nucleotide is made of a phosphate + a sugar + a nitrogenous base. In DNA, the nucleotide is a deoxyribonucleotide (in RNA, the nucleotide is a ribonucleotide).

I-1 Phosphoric acid

Gives a phosphate group.

I-2 Sugar:

Deoxyribose, which is a cyclic pentose (5-carbon sugar). Note: the sugar in RNA is a ribose. Carbons in the sugar are noted from 1' to 5'. A nitrogen atom from the nitrogenous base links to C1' (glycosidic link), and the phosphate links to C5' (ester link) to make the nucleotide. The nucleotide is therefore: phosphate - C5' sugar C1' - base.

I-3 Nitrogenous bases:

Aromatic heterocycles; there are purines and pyrimidines.

- Purines: adenine (A) and guanine (G).

- Pyrimidines: cytosine (C) and thymine (T) (Note: thymine is replaced by uracyle (U) in RNA).

Note: other nitrogenous bases exist, in particular methylated bases derived from the above mentioned; methylation of the bases has a functional role (see chapter ad hoc).

Glossary:

- Nucleoside names: deoxyribonucleosides in DNA: deoxyadenosine, deoxyguanosine, deoxycytidine, deoxythymidine in DNA (ribonucleosides in RNA: adenosine