“We wish to suggest a structure for the salt of deoxyribose nucleic acid (D.N.A). This structure has novel features which are of considerable biological interest.” With this famous understatement, James Watson and Francis Crick announced their discovery of the structure of DNA in Nature on 25 April 1953. Their model, based on Rosalind Franklin’s X-ray diffraction patterns from DNA crystals, finally explained how genetic material could be copied and passed on to future generations. It seeded a revolution that changed biology forever.
But for all its elegant simplicity, the double helix is only part of the story. Watson and Crick worked on pure, crystallised DNA, and you won’t find much of that in living cells. In the real world, DNA is wound, folded and mixed with proteins. This gives it several intricate levels of structure that culminate in chromosomes. Half a century on from the discovery of the double helix, researchers are only just beginning to understand this complex structural hierarchy and determine its biological significance (see “Deconstructing DNA”). This special issue of Â鶹´«Ă˝ brings you the latest research in these areas.
Chromosomes actually contain about twice as much protein as DNA, and it now seems that these proteins have their own code that controls the activity of the DNA wound around them (“Master code”). Massive, mysterious and largely invisible, chromosomes are now starting to show themselves up as being as fussy about their roost in the cell nucleus as any human home buyer (“Location, location, location”).
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The helix itself still holds a few surprises. The fact that it can conduct electricity means DNA has an in-built shield against gene mutations (“Live wire”). One big surprise is that DNA is an extremely unstable molecule. To keep it in shape, and shield us from ageing and cancer, our cells are equipped with armies of enzymes to patch it up (“Running repair”). And the fact that the bases in the double helix always pair with only one partner – adenine with thymine and guanine with cytosine – means that DNA is the ideal information-rich molecule for building the nano-machines of the future (“The robot within”).
Here’s to the next 50 years of discovery.
Deconstructing DNA
From the architecture of a cell’s nucleus, through the double helix, right down to the shape of the bases, the structure of DNA has many levels. Each one plays a vital part in our biology