Friedrich Miescher's isolation of nuclein in 1869

Albrecht Kossel's work on nucleic acid components

Rosalind Franklin's X-ray diffraction images

Watson and Crick's model-building approach

Sugar (deoxyribose)

Phosphate group

Nitrogenous base

Linking of nucleotides in the sugar-phosphate backbone

Adenine with Thymine (A-T)

Guanine with Cytosine (G-C)

Two strands of DNA twisted around each other

Strands run in opposite directions

Structural features of the double helix

Each new DNA molecule contains one original and one new strand

Helicase unwinds the double helix

DNA polymerase adds nucleotides

DNA ligase joins Okazaki fragments on lagging strand

Codes for proteins through the genetic code

Transcription into RNA

Translation into amino acid sequences

Control of gene expression

Epigenetic modifications

Mismatches, breaks, chemical alterations

Mismatch repair

Nucleotide excision repair

Homologous recombination

Non-homologous end joining

Creation of new DNA combinations

Modification of organisms' DNA

Medical treatments

Agriculture improvements

Forensic science