First, a small section of the double-stranded DNA spiral must be made to peel open, exposing the gene’s sequence of nucleotide bases—the alphabet soup of As, Cs, Gs, and Ts you probably remember from your school days. This enables the gene’s DNA sequence to be converted into RNA, a close molecular cousin of DNA. This RNA strand is said to be complementary to the original DNA strand because the new RNA’s As are matched with the original DNA’s Ts; its Cs are matched with Gs. (In truth, RNA uses a nucleic acid denoted by the letter U to match up with DNA’s A, but that’s a minor complication.) Because DNA and RNA share essentially the same nucleic-acid language, biologists call the process of converting DNA into RNA transcription.
Some of these RNA molecules are the end product of the gene, serving the cell with a unique function. But most are just chemical messengers, which carry instructions for the later construction of proteins. So usually the next step is to convert the genetic sequence now coded in messenger RNA into a string of amino acids, the building blocks of proteins. Because there are only 5 nucleotide bases and about 20 amino acids in cells, the language of DNA and RNA is fundamentally different from the language of proteins, which is why biologists call this next stage translation. Via IEEE Spectrum. Image credit Emily Cooper