It Doesn’t Make Any Sense!
Biology (and science in general) has some jargon that sticks around long past the point where they should be buried. “Sense”, for example, is a really popular one. It gave rise to all sorts of derivative words (”anti-sense”, “nonsense”, “mis-sense”), but really those words reflect what geneticists thought of the “DNA code” back in the mid-twentieth century, when they were just beginning to realize that changes in the DNA sequences of genes led to changes in the proteins that were translated from them. The scientists thought of the DNA sequence as the “code” for the protein sequence, but they didn’t know exactly how the two corresponded with each other, which was why all their jargon was very metaphorical: “nonsense”, “commas”, and so on.
“Nonsense” is actually easier to explain than “sense”, so we’ll start with that. Researchers were studying how mutations in genes affected the proteins they coded. Certain mutations, they figured, might scramble the DNA into a sequence that wouldn’t make any “sense” if you tried to translate its code into a protein sequence. Hence, they called these scrambles “nonsense” mutations. Later, however, they found that the “nonsense” mutations didn’t really scramble or garble the instructions for the protein, but that they were just a code for “Stop! This is the end of the protein!” “Nonsense” sequences were naturally occuring “periods” at the end of code “sentences,” so to speak, and the mutations were just putting these periods into the middle of the sentences and truncating them. The cell knew exactly what they meant; they weren’t nonsense at all! But the name stuck, and even today, the particular codons that mark the end of a protein are sometimes referred to as “nonsense codons,” even though the cell knows exactly what they mean.
Of course, scientists, being tinkerers, started to change the endings of the names in order to get new words with related meanings. So if a stop code is called “nonsense”, then everything aside from that is called “sense.” Since there are two strands of DNA, the one that has the code is called “sense”, the other is called “anti-sense” (since “nonsense” is already taken). And if a “nonsense” code mutates to “sense” (or if one “sensible” code mutates to another), then that’s called “missense.” And so on and so forth.
So here we are with this arcane jargon that dates back to the 1950, from before we figured out how genes worked, and yet we’re still stuck with it for historical reasons. It could be worse. We could all still use the word “cistron” instead of “gene.” 
