The scientists James Watson and Francis Crick studied genes in an attempt to find out about their structure. The genetic material DNA (deoxyribonucleic acid) is a complicated molecule, and it had been difficult to understand how DNA could copy itself when cells reproduce. Watson and Crick found that it was shaped like a stepladder twisted into a spiral, and that if the two sides were pulled apart the ‘rungs’ of the ladder would automatically reproduce the rest of the molecule.
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