P.S It's not 7!
Glycine is the only amino acid which is _________.
This is a long shot, but I think it's
Israel is in an odd (5) position.
Glycine has been found in outer space, but Alanine has not. If we replace Croatia with Israel, we get a pattern of two countries that have had citizens in space, then one who has not.
Keeping with the Alanine/Glycine theme from the hint, you can synthesize with the names. enGland mAlaysia sinGapore = GAG; hunGary isrAel venezuelA = GAA, both being the codons for Glutamic Acid.