Protein Translation: Rewrite per discussion

exercises/protein-translation/description.md

@@ -1,36 +1,17 @@
 # Description
 
-Translate RNA sequences into proteins.
+Your job is to translate RNA sequences into proteins.
 
-RNA can be broken into three-nucleotide sequences called codons, and then translated to a protein like so:
+RNA strands are made up of three-nucleotide sequences called **codons**.
+Each codon translates to an **amino acid**.
+When joined together, those amino acids make a protein.
 
-RNA: `"AUGUUUUCU"` => translates to
-
-Codons: `"AUG", "UUU", "UCU"`
-=> which become a protein with the following sequence =>
-
-Protein: `"Methionine", "Phenylalanine", "Serine"`
-
-There are 64 codons which in turn correspond to 20 amino acids; however, all of the codon sequences and resulting amino acids are not important in this exercise.
-If it works for one codon, the program should work for all of them.
-However, feel free to expand the list in the test suite to include them all.
-
-There are also three terminating codons (also known as 'STOP' codons); if any of these codons are encountered (by the ribosome), all translation ends and the protein is terminated.
-
-All subsequent codons after are ignored, like this:
-
-RNA: `"AUGUUUUCUUAAAUG"` =>
-
-Codons: `"AUG", "UUU", "UCU", "UAA", "AUG"` =>
-
-Protein: `"Methionine", "Phenylalanine", "Serine"`
-
-Note the stop codon `"UAA"` terminates the translation and the final methionine is not translated into the protein sequence.
-
-Below are the codons and resulting amino acids needed for the exercise.
+In the real world, there are 64 codons, which in turn correspond to 20 amino acids.
+However, for this exercise, you’ll only use a few of the possible 64.
+They are listed below:
 
 | Codon              | Amino Acid    |
-| :----------------- | :------------ |
+| ------------------ | ------------- |
 | AUG                | Methionine    |
 | UUU, UUC           | Phenylalanine |
 | UUA, UUG           | Leucine       |
@@ -40,6 +21,18 @@ Below are the codons and resulting amino acids needed for the exercise.
 | UGG                | Tryptophan    |
 | UAA, UAG, UGA      | STOP          |
 
+For example, the RNA string “AUGUUUUCU” has three codons: “AUG”, “UUU” and “UCU”.
+These map to Methionine, Phenylalanine, and Serine.
+
+## “STOP” Codons
+
+You’ll note from the table above that there are three **“STOP” codons**.
+If you encounter any of these codons, ignore the rest of the sequence — the protein is complete.
+
+For example, “AUGUUUUCUUAAAUG” contains a STOP codon (“UAA”).
+Once we reach that point, we stop processing.
+We therefore only consider the part before it (i.e. “AUGUUUUCU”), not any further codons after it (i.e. “AUG”).
+
 Learn more about [protein translation on Wikipedia][protein-translation].
 
 [protein-translation]: https://en.wikipedia.org/wiki/Translation_(biology)