Nucleic acids structure is classified into four categories. They are explained below –
1. Primary Structure
The main structure of the nucleic acids contains the linear sequence of the nucleotides. These nucleotides are connected to one another by the phosphodiester linkage system. The three most important constituents of nucleotides are phosphate groups, the nitrogenous base, and 5-carbon sugar.
The nitrogenous base contains purines; adenine, guanine and pyrimidines; thymine, cytosine, uracil. The 5-carbon sugar contains deoxyribose (DNA) and ribose sugar (RNA).
The purine bases create the glycosidic link between their 9’ nitrogen and the 9’ – sugar molecule (OH group). Pyrimidine bases, on the other hand, create the glycosidic bond between the 1’ nitrogen and the 9’ – deoxyribose (OH group).
The purine as well as the pyrimidine bases the phosphate group creates a link with the sugar molecule. The nucleotides create the phosphodiester bond between the 5’ and 3’ carbon atoms, which forms the nucleic acids.
An example of complementary sequence AGCT is TCGA.
2. Secondary Structure
The interaction between the bases forms the secondary structure of nucleic acids. It signifies the portions of the strands, which are linked to one another. The two strands of DNA (double helix of the DNA) are related to one another according to the hydrogen bonds. The nucleotides on one strand are linked to their counterparts on another strand. When it comes to the pairing of the two-polynucleotide strands, the secondary structure is the key to forming a double helix.
3. Tertiary Structure
The tertiary structure form is the base, the three-dimensional shape that forms the entire chain. The four key forms of tertiary structure are as follows:
- The extent of the helix turn
- The number of pairs per turn depending on base
- Right/left handedness
- The variance in size between the major and minor channel
4. Quaternary Structure
The quaternary structure is the advanced level formation and organization of the nucleic acids. This particular structure defines the interactions of the nucleic acids with different molecules. The most common organization is the form of chromatin.