Dna structure

Science

Definition

DNA (deoxyribonucleic acid) is a double-stranded molecule shaped like a twisted ladder, called a double helix. Each strand is made of nucleotides containing a phosphate group, a deoxyribose sugar, and one of four nitrogenous bases (adenine, thymine, guanine, cytosine) that pair according to complementary base pairing rules (A-T, G-C).

Examples

  • Watson and Crick's 1953 model showed the double helix structure using X-ray data from Rosalind Franklin
  • Forensic DNA fingerprinting relies on unique sequences within a person's DNA structure
  • The human genome contains approximately 3 billion base pairs organized into 23 pairs of chromosomes
Key Fact

A pairs with T (2 hydrogen bonds); G pairs with C (3 hydrogen bonds). Strands run antiparallel (5'→3' and 3'→5').

Related Terms

Dna replication Transcription Macromolecules Hydrogen bonding

Study This Concept

Practice DNA structure with free review games in these units:

Biology Unit 4: DNA and Protein Synthesis