Question

What is DNA replication? Write the chemical composition of DNA?

Answer 1

The term replication means an action of copying or reproducing something. DNA and RNA are two types of nucleic acid. DNA acts as genetic material in most organisms and passes information from one generation to another generation. DNA is more stable than RNA. DNA as an acidic substance present inside the nucleus was identified by Friedrich Meischer.

Complete answer:
DNA replication is a biological process of producing two identical replicas or copies of DNA from one original DNA molecule, which works as a template.
This process occurs in all living organisms and is the basis for inheritance.
During replication, the two strands separate and act as a template for the synthesis of new complementary strands.
During each replication, one new strand is formed and one old stand remains intact, that's why replication of DNA is called semi-conservative in nature.
Matthew Meselson and Franklin Stahl give experimental proof of the semi conservative nature of DNA replication.
CHEMICAL COMPOSITION OF DNA-
DNA also known as deoxyribonucleic acid is a polymer chain of nucleotides. It is formed by joining numerous nucleotides.
A nucleotide is composed of three components-
Nitrogenous Base
Pentose Sugar
Phosphate group
Nitrogenous base- Nitrogenous base is a molecule that contains nitrogen in them and has properties of base. There are two types of nitrogenous base-
Purine- Adenine and Guanine are two purine bases present in DNA.
Pyrimidine- Thymine and Cytosine are two pyrimidines present in DNA.
Pentose sugar- This is a cyclic carbohydrate made up of five carbons. The pentose sugar found in DNA is called deoxyribose sugar. The -OH group is absent at 2’ position of ribose in them.
Phosphate group- Phosphate molecule $PO_4^{3-}$ forms a link with 5’ carbon of deoxyribose sugar.

Note:
DNA is a double helix structure. It is made up of two-strand which have antiparallel polarity.
The nitrogenous bases in two strands are joined through Hydrogen bonds. Adenine forms two hydrogen bonds with Thymine and vice versa. Similarly, Guanine forms three hydrogen bonds with Cytosine. Purine always forms bonds with pyrimidine thus forming a uniform distance between the two strands of DNA helix.