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Learn the toughest concepts covered in Biochemistry with step-by-step video tutorials and practice problems by world-class tutors

Review 1: Nucleic Acids, Lipids, & Membranes

Practice - Nucleic Acids 3


Nucleic Acids 3

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if you haven't yet answered. Question 10. Pause the video now and try it. If you have ribose or deoxyribonucleic for that matter and it's linked thio a base like Adnan, for example. What you have is a nucleoside, right, because the side ending, as opposed to the tide ending, means that there's no phosphate group here. So looking at our molecule that we are given, which is again ribose attached to you, Adnan, we would call that molecule Dennis scene. That's the name of that particular nucleoside. It would not be a deoxyribonucleic aside because we're using ribose, not deoxyribonucleic, while adding is appearing. It's not a nucleotide because there's no phosphate group present. And likewise C is wrong because it's not nucleotide. And also add means not even a pie remedying. So it's like double wrong. And a Dennis ing mono phosphate implies that there's a phosphate group attached, which there's not. So that's out to leaving us with E. Looking at Question 11 the double helix form of DNA is stabilized by de non specific base stacking interaction between two adjacent bases in the same strand. So if we look at a strand of DNA that saying that the two bases along one strand have an interaction between them, and here are two bases on the other strand. So if we kind of zoom in on this image, basically are bases air kind of stacked on top of each other, and they have thes stacking forces that are holding them together. And these are in fact, hydrophobic forces. But it's worth noting that water interacts with the outside of DNA drawing little water molecules here. And you might remember that the outside of DNA has all those phosphate groups on it, which are negatively charged, meaning water is gonna play nice with them. So those were actually Hydra Filic forces that helps stabilize the structure as well just on the outside, as opposed to the inside. And just looking at the wrong answer choices. Real quick Covalin bonds between the three prime end of one strand, the five prime of the other. Nope. There's a phosphate group in the middle there. Right? Um, do you have that fostered Iast your bond? Um, and looking at B A hydrogen bond between the phosphate groups? No, we have hydrogen bonding between the bases. Hydrogen bonds between the ribose again no hydrogen bonds between the bases and ribose interactions with the planer base pairs while their co violently bonded. That's about it. So on again, all those don't help stabilize the structure. So D is the correct answer. Looking at question 12 double stranded RNA takes on a form and a forms and be forms are right handed. Always those air right handed Helix Z is a left handed helix, so double stranded RNA takes the A form. B form is what we find most DNA in, and we see the Z form around regulatory sequences. All right, looking at 13 what is the complementary strand to the one given? Well, I've given you a little hint by including the five prime and three prime up there because, remember, DNA has always written five prime to three prime. So, well, a might look like a good answer. It is actually a trap. And that's because here is our five prime and and here is our three prime end B is the correct answer. He is the correct answer, and that is because if we write it backwards, we have our three prime end t a a see g t a and by Prime, and you can see that that is complimentary to the Strand. Given there. Now it's worth noting that this question could have been fair game without the three prime. The five prime indicated you're supposed to know that stuff right? When DNA is heated to about 95 degrees Celsius, which change does not occur. And while UV light absorbent does increase right, this is called the hyper crow Makeshift Blake aside, Bonds do not break. Those will stay together. Those air pro Vaillant Bonds they're really strong. They're not gonna be broken down by temperatures of temperatures that are that low. The helix will unwind, right? The DNA is gonna de nature and the strands they're gonna separate, which means that the hydrogen bonds between the bases air gonna break. And additionally, the viscosity of the solution will decrease. That's not really a fact. You need thio worry about too much. A. The facts in a C and D are much more important for you to understand. So, looking at question 15 in a DNA, um, in DNA sequencing by the classical Sanger method what the answer is D the role of diet, the oxy CTP is to occasionally terminate formation of the complementary strand. All the di di Oxy nucleotides are used in order to terminate formation of the complementary strand early so that we developed fragments of different lengths. A is wrong because we wouldn't include the same diet. Deac Si, nucleotide. In all four reaction mixtures we would Onley included in we would include one in each right, So we'd have one That's a one that is t one that s C and one that is G and it doesn't necessarily have to be. You know that particular order But they're done separately from each other. Specific enzymes are used to cut the product into smaller pieces. No, the pieces are made because of early termination of synthesis. You know, we use a much smaller concentration. He was like millimeter er concentration of DNT ps and like micro Moeller concentration of ddn TPS. And so every now and then, one of these di di oxy nucleotides is added and because it lacks a three prime hydroxyl group, synthesis can't continue on that strand. So you get early termination. So you wind up with fragments of the whole strand that you're trying to replicate dieting. ACSI nucleotides are present at low levels. Right? Milliman are Micro Mueller compared to minimal or much, much smaller, like over 1000 full difference. And, um, the template strand is radioactive, so that can cleave the product into small pieces. This is nonsense, uh, way use radioactively labeled di di oxy nucleotides so that we can figure out, you know, like which strands they're attached to you and, you know, use it to read them on gels. But the radio activity is just in order to identify the molecules, not Thio cut anything. It's not really how radio activity works anyways. Uh, with that let's flip the page.