Structure of DNA
1) Double Helix
DNA is composed of two long strands that form a double helix, which looks like a twisted ladder.
Backbone: Each strand consists of a sugar-phosphate backbone, with the sugar being deoxyribose.
Bases: Attached to each sugar is one of four nitrogenous bases: adenine (A), thymine (T), cytosine (C), and guanine (G).
Base Pairing: The strands are held together by hydrogen bonds between the bases, with A pairing with T and C pairing with G.
2) Antiparallel Orientation
The two strands run in opposite directions, one from 5' to 3' and the other from 3' to 5'.
3) Major and Minor Grooves
The twisting of the helix creates grooves, which are the sites of protein binding for replication and transcription.
4) Chromatin and Chromosomes
DNA is packaged into chromatin, which further condenses to form chromosomes during cell division.
Functions
Genetic Information Storage: DNA holds the genetic blueprint for the development, functioning, and reproduction of all living organisms and many viruses.
Replication: DNA can replicate itself, ensuring that genetic information is passed from cell to cell and from generation to generation.
Gene Expression: DNA sequences (genes) are transcribed into RNA, which then directs the synthesis of proteins.
Regulation: DNA contains regulatory sequences that control the expression of genes, influencing when, where, and how much gene product is made.