DNA, the Language of Evolution:
Francis Crick & James Watson (2 of 2)

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Life’s Cookbook
In the years that followed, Watson, Crick, and other researchers figured out the basics of how DNA works. Each gene, they realized, consists of a stretch of base pairs. A single-stranded copy of the gene was created (known as messenger RNA) and transported to protein-building factories in the cell called ribosomes. There, the sequence of the bases guided the assembly of a string of amino acids that became a new protein. When a cell divides, the double helix is unzipped and the DNA is replicated. It is life’s cookbook.

Using DNA
Evolutionary biology was revolutionized by the discovery of DNA. Mutations, researchers realized, change the spelling of the cookbook. A single base pair may change, or a set of genes may be duplicated. Those mutations that confer a selective advantage to an individual become more common over time, and ultimately these mutant genes may drive the older versions out of existence.

The structure of DNA

Thanks to the discovery of DNA, it is now possible for scientists to identify not just the genes, but the individual bases. Before the discovery of DNA, scientists could only uncover the evolutionary tree of life by comparing the bodies and cells of different species. Now they can compare their genetic codes, working their way down to the deepest branches of life dating back billions of years.

• DNA structure after an illustration at DOEgenomes.org.

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Spanish translation of Understanding Evolution For Teachers from the Spanish Society of Evolutionary Biology.