DNA Double Helix & Base Pairing

The molecule that carries life's blueprint

DNA (deoxyribonucleic acid) is a double-stranded helix where two polynucleotide chains coil around each other. Each strand is a polymer of nucleotides, each containing a deoxyribose sugar, a phosphate group, and one of four nitrogenous bases: Adenine (A), Thymine (T), Guanine (G), or Cytosine (C). The strands are antiparallel and held together by hydrogen bonds between complementary bases (A-T, G-C). The genetic code is read as triplets (codons) along one strand. During replication, helicase unzips the helix and DNA polymerase synthesizes new complementary strands — producing two identical daughter molecules (semi-conservative replication).