I. Introduction

• DNA (deoxyribonucleic acid) is a molecule that encodes the genetic information of all living organisms.
• Discovered by James Watson and Francis Crick in 1953, it has become one of the most studied and important molecules in biology.

II. Chemical Composition

• DNA is made up of four nitrogenous bases: adenine (A), cytosine (C), guanine (G), and thymine (T).
• These bases are linked together by a sugar-phosphate backbone.
• The sugar in DNA is deoxyribose and the phosphate group creates a bond between the sugar molecules.

III. Double Helix Structure

• The most famous aspect of the DNA structure is its double helix shape, which resembles a twisted ladder.
• The two strands of the DNA molecule run in opposite directions, with the nitrogenous bases forming the rungs of the ladder.
• The hydrogen bonds between the nitrogenous bases hold the two strands together.
• A base pair is formed by two nitrogenous bases, one from each strand, and the base pairing rules are A-T and C-G.

IV. Chromosomes

• In eukaryotic cells, DNA is packaged into structures called chromosomes.
• Each chromosome contains a single, very long DNA molecule and associated proteins.
• The chromosomes are responsible for the proper segregation of DNA during cell division.

V. Replication

• Replication is the process by which DNA is copied, allowing it to be passed on to daughter cells during cell division.
• Replication begins with the unwinding of the double helix and the separation of the two strands.
• New nucleotides are then added to the single strands, with complementary base pairing ensuring that the new strand is a perfect copy of the original.

VI. Conclusion

• In conclusion, DNA is a complex and fascinating molecule that plays a crucial role in the biology of all living organisms.
• Its double helix structure, chemical composition, and ability to replicate make it a vital part of genetics and the study of life.