Much improved. I can kind of understand what I'm doing now. I don't think it's really teaching me anything that I'll remember because it feels like it's skipping over a lot of details and just giving a few cues (which probably is good for the game). Now that I can actually read the text, and presumably the UI has been improved, the game is playable.
It does seem like a relatively easy puzzle game (so far!), but it might be a good game for kids. It's probably still a bit too advanced for my nephew, but in a year or two he might be able to figure it out with help.
Side note: The Reverse Complement button text seems to flow off of the button (not sure if you knew and didn't care or if it's environmental).
I found this part difficult to comprehend (perhaps because the button graphics are broken?), but I guess I figured it out with a bit of scratching.
I take it back. This is not appropriate for kids. It hurts my head.
For example, the game does not give any kind of persistent hint about what a "stop codon" is or any tricks for remembering all of this. So somehow I just have to remember these 3 sequences? I have adult things filling my brain up at the moment. I think you should try to make this easier for the player (whether you give visual hints, or show hints when I press ?, or explain how it works so it can be figured out on the fly, or just explain some tricks that people use to keep it straight).
Somehow I fixed it, but the UI still looks like the puzzle isn't solved. I don't understand.
I apparently managed to complete the game, but I obviously didn't fully understand parts of it still. As a side note, the game should not quit when you complete it. Instead, it should return you to the menu screen. It would be OK to present credits there too and prevent the player from skipping over it for a few seconds). I barely caught that the game was over. Had I missed it, I might have thought that the game crashed instead.