WEBVTT 00:00:08.466 --> 00:00:09.316 >> Dude: Hey Sally. 00:00:09.556 --> 00:00:10.226 >> Sally: Hmmm? 00:00:10.226 --> 00:00:12.546 >> Dude: How come Buddy is green and I'm not? 00:00:12.766 --> 00:00:13.356 >> Sally: Well Dude. 00:00:13.356 --> 00:00:16.786 Your parents aren't green and I'm guessing that Buddy's parent was. 00:00:16.896 --> 00:00:20.206 >> Dude: That's not what I mean...like, what makes him green? 00:00:20.466 --> 00:00:20.966 >> Sally: Envy? 00:00:21.346 --> 00:00:23.796 >> Dude: Fine, I'll figure it out myself. 00:00:25.156 --> 00:00:27.526 Alright! Here it is. 00:00:27.666 --> 00:00:30.046 Hey Sally, check this out. 00:00:30.266 --> 00:00:31.876 All of Buddy's DNA is online. 00:00:31.966 --> 00:00:34.516 Now all I have to do is find the part that makes him green. 00:00:35.526 --> 00:00:38.636 What a nightmare. 00:00:37.066 --> 00:00:38.036 It all looks the same. 00:00:38.036 --> 00:00:39.846 Just Gs, As, Ts, and Cs. 00:00:39.846 --> 00:00:42.026 How am I suppose to know what's what? 00:00:42.376 --> 00:00:44.656 Someone needs to write a manual. 00:00:44.926 --> 00:00:47.376 >> Sally: We are writing one, but it's a work in progress. 00:00:47.676 --> 00:00:48.876 Why is Buddy green? 00:00:48.966 --> 00:00:52.266 Well, it's probably because he makes a protein or two that turn him green. 00:00:52.566 --> 00:00:57.336 We can figure that out, because sequences that code for proteins have a few things in common. 00:00:57.976 --> 00:00:59.626 >> Dude: Oh I remember now. 00:00:59.826 --> 00:01:05.046 They all start with ATG then call out for amino acids using three bases at a time. 00:01:05.316 --> 00:01:07.676 >> Sally: Those 3 bases are called triplet codons. 00:01:08.016 --> 00:01:10.916 Here's a look up table with the genetic code for Buddy. 00:01:11.336 --> 00:01:14.836 It tells you which amino acids are encoded by each triplet codon. 00:01:15.076 --> 00:01:16.436 >> Dude: OK I got it now. 00:01:16.726 --> 00:01:22.366 Here's an ATG for the methionine start, then I see a TAT, that translates to tyrosine, 00:01:22.545 --> 00:01:25.696 then TAG that will make a ...stop? 00:01:26.295 --> 00:01:27.606 That's only two amino acids. 00:01:27.906 --> 00:01:29.876 That seems too short to do anything in the cell. 00:01:30.136 --> 00:01:32.536 >> Sally: You've just figured out something really important. 00:01:32.696 --> 00:01:34.496 Not every ORF will make a protein. 00:01:34.946 --> 00:01:39.956 As a rule of thumb, people consider 100 amino acids the minimum to produce a protein, 00:01:40.326 --> 00:01:43.265 even though there are lots of proteins we know that contain fewer. 00:01:43.556 --> 00:01:47.436 >> Dude: Did you say ORF or did you just burp? 00:01:47.856 --> 00:01:49.056 >> Sally: didn't burp! 00:01:49.376 --> 00:01:51.246 ORF stands for open reading frame. 00:01:51.376 --> 00:01:57.406 It's a register for reading the section of DNA that starts with ATG, uses 3 letters at a time 00:01:57.406 --> 00:02:02.776 to call for amino acids and then uses one or more of the stop codons to close the reading. 00:02:03.056 --> 00:02:06.746 >> Dude: So in this DNA sequence there are 3 reading frames that I have to look through? 00:02:07.256 --> 00:02:08.386 That will take me forever. 00:02:08.756 --> 00:02:13.506 >> Sally: Actually it will take you forever times two since there are 6 reading frames. 00:02:13.616 --> 00:02:18.036 Remember DNA is double stranded and the bottom strand, the one you're not seeing here, 00:02:18.076 --> 00:02:20.076 might also have ORFs that make proteins. 00:02:20.176 --> 00:02:23.076 >> Dude: Please tell me there are computer programs to help me with this. 00:02:23.166 --> 00:02:26.776 >> Sally: There are lots of good ones, but once you find all the ORFs what will you do? 00:02:27.186 --> 00:02:29.046 >> Dude: Yeah...then what? 00:02:29.166 --> 00:02:31.786 How will I know which of the ORFs really make proteins? 00:02:31.786 --> 00:02:32.866 And what if I've missed a bunch? 00:02:32.976 --> 00:02:36.766 Maybe some proteins that turn Buddy green are only a few amino acids long. 00:02:36.836 --> 00:02:37.526 >> Sally: Nice! 00:02:37.526 --> 00:02:40.166 You've got the start of a really interesting project here. 00:02:40.536 --> 00:02:44.146 But remember that discovering important proteins is only part of your job. 00:02:44.516 --> 00:02:48.536 If you really want to engineer biology you'll have to refine the genetic material 00:02:48.766 --> 00:02:50.305 so you and others can build with it. 00:02:50.626 --> 00:02:53.436 Before Buddy wakes up, can I show you one great example?