Biochemical Gallery

Watson and Crick, DNA discovers

Watson and Crick. Caricature of the molecular biologists and discoverers of the structure of DNA James Watson (born 1928, left) and Francis Crick (1916-2004), with their model of a DNA molecule. Watson, an American, and Crick, British, met at the Cavendish Laboratory, Cambridge, in 1951. Their work on DNA was performed with a knowledge of Chargaff's ratios of the bases in DNA and access to the X-ray crystallography of Maurice Wilkins and Rosalind Franklin at King's College London. Combining this knowledge led to the deduction that DNA exists as a double helix. Crick, Watson and Wilkins shared the 1962 Nobel Prize for Physiology or Medicine, Franklin having died in 1958

© GARY BROWN/SCIENCE PHOTO LIBRARY

DNA nucleosome, molecular model

DNA nucleosome. Molecular model of a nucleosome, the fundamental repeating unit used to package DNA (deoxyribonucleic acid) inside cell nuclei. DNA is the molecule that carries the genetic code that forms the basis of all life on Earth. It is a long molecule and has to be tightly coiled to fit inside the nucleus. DNA's double helix structure is shown here as a coiled orange spiral. The DNA is coiled round a core of histone proteins (multicoloured ribbons). The ribbons represent the molecular structure of the histone proteins. Each set of two DNA loops around a histone core is known as a nucleosome. Further compacting and packaging (not seen here) form the denser forms of chromatin, and eventually the cell's chromosomes

© LAGUNA DESIGN/SCIENCE PHOTO LIBRARY

HIV reverse transcription enzyme

HIV reverse transcription enzyme. Molecular models of the reverse transcriptase enzyme found in HIV (the human immunodeficiency virus). The foreground model shows the helices and arrowed sheets representing the enzyme's shape (secondary structure). The background model shows the 7844 atoms (spheres) of the molecular structure. Reverse transcriptase is an enzyme that is a key part of the process of producing DNA (deoxyribonucleic acid) from the instructions contained in a strand of RNA (ribonucleic acid). Many viruses, including HIV, consist of a core of RNA, and this reverse transcription is how HIV infects human cells. This enzyme is from the HIV-1 form of HIV, the virus that causes AIDS (acquired immune deficiency syndrome)

© LAGUNA DESIGN/SCIENCE PHOTO LIBRARY