When you form this covalent bond,,, those covalent,,, you just end up with sugar phosphate-sugar phosphate. This molecule up here could be a thymine or a guanine. Now, an important question is this molecule symmetrical. No, it isn't it has a specific direction. This molecule is called something very specific. Let's go back to organic chemistry, remember, the numbers. There's a phosphate group off that carbon. Draw a P around it to show that. The important part is cabon 3 that has the hydroxyl group down here. Remember dehydration synthesis. You don't have to draw this, you just have to be able to identify it. Questions guys? In organic chemistry, we always number the functional groups and molecules. You can have many thousands of.... we have our strand of DNA, but what is wrong with this piece of DNA. DNA is not single-stranded, it is double. DONT DRAW THIS DO NOT DRAW WHAT I AM ABOUTTO DRAW IT IS WRONG just look. Purines have to match up with Pyrimidines. DONT DRAW THIS IM GOING TO ERASE IT. SO does hydrogen and guanine work. Yes. DOes anyone see what the problem is going to be? Its going to be a number 3 hydroxyl group if this is g thaen what does this have to be. Do you guys see an issue? Flip it. This is a t, we need something to match up with it, an A. This part id where I really earn my money <b>draws someting</b> Whew there we go, it's upide down. Heres the 3 prime OH.