Structure of DNA
- DNA is formed by the joining of many nucleotides. These nucleotides are called monomers.
- Phosphate and sugar in DNA are linked together by ester bonds. It is arranged in an alternate order.
- Nitrogen bases are linked to each other by H-bonds and to sugars by glycosidic bonds.
- Nitrogen bases are arranged on top of each other in the form of a layer to form a polynucleotide chain.
- The following types of structures are possible in DNA.
1. Primary Structure –
- In this, nucleotides are joined by phosphodiester bonds to the 5′ and 3′ carbon molecules.
- In this, the chain is represented by the first letter of the base. Whose 5′ end is towards Left.
- Ex. – A-G-C-T-T-A-C-A
2. Secondary Structure –
- In this, bases of ssDNA (Primary Structure) are joined by hydrogen bonds with bases of other ssDNAs. From which dsDNA is formed.
- Nucleotides in this DNA join at special bond angles to form a spiral structure.
3. Tertiary Structure –
- In this, the dsDNA becomes hypercoiled to form a 3D structure.
- The double helix chain of DNA is tertiary structure, which is found in different forms.
- Eg – B-DNA, ADNA C-DNA Z-DNA
4. Quaternary Structure –
- The tertiary structure becomes hypercoiled again. Due to which Nucleoprotein and Nucleosome are present.
- It again forms a super coiled structure by forming a loop. Which is called chromatin.