hello and this is chapter 6 on dna well actually it's called nucleic acids and protein synthesis now um it is one of my favorite topics to teach and talk about and i love it so much and it's because it is complex but it's not too complex and it's elegant and it's beautiful okay sorry i'll stop learning now let me give you a chapter outline of um this chapter there are going to be five videos in total um part one has three videos whereas part two has two videos three videos on part one the first one which is this one will be on structural nucleotides rna and dna and then we'll talk about this three channel dna replication don't worry about it and um the last one is actually about the most beautiful biology experiment ever i it's really cool but we'll get there we'll get there part two is what protein synthesis transcription and translation [Music] and gene mutation will be the last video okay so let's jump straight in into the material this is introductory genetic materials and genetic materials are found in all cells all organisms sorry not all cells but all organisms it is either dna or rna but you surely have them and they have two main characteristics the ability to carry information and the ability to be copied now whatever we're going to learn about dna together is discovered by these two guys james watson and francis creek and and they published this paper in 1953 so it hasn't been discovered that long if you think about it it's only been like what 60 something years um it is not that long ago but we science has expanded and come a long way but anyways back to this watson and creek fellas we always use the last names watson in quick's dna structure and paper was actually quite controversial during that time no one um it was really it was a breaking a breakthrough at that point of time and they even won like a nobel prize with but it was very controversial because they stole um experimental results without consent from other scientists like roseanne franklin and did not even credit her in their write up at the end absolutely annoying um anyways yeah rosalind franklin she of course was a female scientist and at the point of time female scientists were not that common um and therefore she was marginalized even in her lab anyways um that story is very interesting and you can read up yourself later it is definitely not in syllabus okay back to the point about genetic materials now every organism does have some form of genetic material and it can carry information and all of them are in the form of nucleic acids how fascinating is that nucleic acid is um a general term like biomolecules we have protein carbohydrate lipids nucleic acids is just one of them and the monomer is nucleotides i'm just going to speed ahead the polymer is called poly neutral types although no one really calls it that there are two types one is dna and two is rna we use dna rna much more often than we do poly nucleotides right anyways let's go backtrack a little bit the bond between adjacent monomers so when nucleotide binds with nucleotides they form phosphodiester bond but nucleotides also have this thing called complementary base pairs and you will learn more detail later but complementary base pairs is just the idea that a binds to key and c binds to g so a binds to t and c minus g those are complementary base pairs and um between them it's not phosphodiester bond it is hydrogen bond more on that later now let's talk about the the the components that make up nucleotide this is the monomer okay so first of all you need a nitrogenous base it could be purine or pyrimidine you'll need that data a pentose sugar it could be deoxyribose or ribose and at last but not least a phosphate group which is negatively charged now nitrogenous base um we have two major types right purine and pyrimidine purine um consists of adenine and guanine whereas purine sorry whereas pyrimidine has cytosine uracil and thymine so so far you know all these five names right are cytosine uracil tiny but they are actually separated into these two major types now we remember i used the terms pure as also purine adenine and guanine inside a and g and pyrimidine has cut cytosine uracil and thymine now cut is not really cut but cut means shorter right so i think of shorter as having one ring only whereas purine has two rings now you might be wondering why in the world do we have to learn two categories don't we just need to know the five names why can't we just learn the five names that's because they are different in structure there's one so alien bonding has two rings and the rest we have one name and the fact that human always binds with pyramiding and that's pretty important purine always binds with pyrimidine so adenine which is a purine will bind with timing which is a pyramiding guanine that is a purine will always bind with sanosing which is a pyrimidine right and they always have these um formation purine with pyrimidine and this is important because dna molecule can have the same rift well so you won't have to fat two rings two two rings binding together but always a two-ring molecule binding with a one ring nitrogenous base touring nitrogenous base combining with a one ring nitrogenous base resulting in three rings right and always three rings so same with trump now that's just nitrogen's pairs um let's talk a little bit about go back a little bit and talk about um the pentose sugar pentose sugar is a five carbon sugar and as we said just now it can have either deoxyribose or ribose now what is the difference between these and you do need to know um so pretension deoxy means less one oxygen right deoxy means don't have oxygen so cancer sugar on the second carbon here doesn't have oxygen just a hydrogen whereas the second carbon here you can see here driver of rubbish sugar has oh it has one more oxygen at them than the oxygen deoxy fibers okay with that opening now we are ready to talk about polymers so the monomer is a nucleotide the polymer is a polynucleotide again we don't usually say polynucleotide we say rna or dna in general now rna this should not be near to you rna is ribonutric acid and is a single stranded molecule it actually forms a single helix like in this pattern now of course its nucleotide is similar well has is the same except that it has arrival sugar and um this ribose sugar contains one oxygen at the more than the oxymethols it's important to note that rna doesn't have thymine but has uracil by the way looks like it's telling you that hey you know a rna molecule and you have been using the name very often throughout chapter one and two and three and four actually atp now atp is actually a rna nucleotide by the way it doesn't form a polyneurotype but it doesn't form a long chain but it is actually um made out of one ribose sugar so it's a rna nucleotide in adenine nitrogen space in three phosphate groups you will realize that some drawings have three phosphate groups some drawings only have two or one for rna for types in general and we will find out why as we go along okay that is rna very brief um we'll go into more details of rna and details of different types of rna as well in the next chapter well in the next part let's talk about dna molecules again this is this should not be new to you should we recap dna stands for d oxy ribonucleic acid it is double stranded and forms a double helix and it has complementary base pairs between those two strands it is definitely longer than rna and again the difference is just in the nucleotides as well right there there are differences in the nucleotides as well you can use dna nucleotides no problem you do not need to write d oxy vibro nucleotides such a long easily misspelled word again is mostly the same except that it has deoxyribose sugar which contains one oxygen less than ribose the bases here are thymine adenine and bonding again timing is present here but uracil is not now the structural differences between rna is a common question and you better know them by heart if not i'll have this face here the kalisi um i ain't going to have his hair though i'm not going to remind you that during the exams okay so here comes a new part and here comes the made more heavy part of this chapter the structure of dna sorry the more heavy part of this video just this video usual dna it's important to remember that the linking of neutral text occurs in the nutrients throughout phase because in s phase that is a synthesis phase a synthesis of what dna and during the synthesis of dna you will have these reactions this reaction right one over here and the monomer here together joins together um and forms a phosphodiester bond this is a condensation reaction s h2o is um the product of this reaction as well now it's because of this phosphodiester bond formation that dna forms a sugar phosphate backbone what do you think what what do i mean by so sugar phosphate backbone right actually it's this so you look at these two molecules here these two molecules that are joined together here and you realize that if we follow um the backbone of the molecule okay follow the parts that are connected there's a phosphate group here and then it's connected to sugar let's collect a phosphate and another sugar let's do the next slide um then come back again this is phosphate sugar phosphate sugar and they're more for sweet sugar phosphate sugar and this thing is called sugar phosphate and there's both sides of the dna both strands of the dna have this sugar phosphate backbone now these are strong covalent bonds means that these bonds are not easily broken they are very strong and that's why it's called the backbone of dna it really keeps the structure stable now the second thing we need to know is complementary base pairing that occurs so you already know what it is let's talk about it in more detail complimentary base pairing is basically the idea that a binds to t and g applies to c now in addition to that we need to know that hey it's hydrogen bonds that's going to them together hence hydrogen bonds um of a particular number as well so a bunch of t and between them there are two hydrogen bonds and there are three hydrogen bonds between g and c so i think of three g c they all rhyme and t2 a well t and two sort of start with t so and they sound similar to well it works for me um 3g c sounds like this love in the world so anyways you can find your own way as well um complementary base pairing occurs between these opposite strands and it always points to g and g by g always binds to c and it's important that they are bound in this specific way um why we'll talk about it later now the hydrogen bonds because they occur between the opposite strand actually holds the two strands together and keeps them from separating the blue strips here would symbolize um the sugar phosphate backbone and there would be for hydrogen bonds occurring between these nucleotides we'll talk about that later now this parent of bases again is always very precise um again two hydrogen bonds between a and t so a cannot form correctly hydrogen is correct use torsion it can't really form bonds properly with guanine as well or g it's always very precise and again purine always binds with pyrimidine there's always t binding um it's always a which is a purine that binds to pyrimidine and this causes the distance between strands to stay the same organism why is it so important to have hydrogen bonding holding it together why can't it be like other kinds of bonds well it's because it is important for the 3d structure and also important for the replication transcription remember what we said um back in the two that hydrogen bonding is um individually weak but cumulatively strong which means individual hydrogen bonds are weak but cumulatively is pretty stable so it's important for 3d structure because there are so many hydrogen bonds and it holds the two strands together and gives some stability but individual hydrogens are still weak compared to other kinds of bonds so strands can be separated this is important for the replication and or transcription because in those in those processes as we will see later um they are um [Music] they need to be separated quite often hydrogen bonds only form between specific bases okay which means there will be fewer mistakes in replication and transcription and hydro bonds also can easily form without a chemical reaction it is a spontaneous thing it does not require an enzyme which makes it easy um i think we will get a full picture of why it's so important for dna replication and transcription um when we finish those processes then when we finish those processes feel free to come back here and take a look at this again okay so so far we've talked about two things about the dna number one is the idea that it has a sugar phosphate backbone number two is the idea that it has this complementary base pairs and hydrogen bonds between them and number three is the idea that they are anti-parallel they realize that one strand um is running from five prime to three prime and the other is 3.25 prime wait hold on i didn't explain what empty parallelized antiparallel is not parallel it is a fancy word for opposite so anti-parallel means the dna strands run in opposite directions then you might be thinking what in the world is five prime to three point when the wall is true prime to five prime okay let me explain to you now prime is actually a short form we usually use for carbon so if it's number one carbon number one we say is one prime is often used in chemistry all right so you remember a deoxyribose sugar it has five carbons so you have one prime here clockwise always after the oxygen one prime two prime three prime 4.5 prime okay got that in mind now if you look at this enlarged image of the same thing you realize that five prime n is nearest to carbon five so believe me let's label them so clockwise after oxygen atoms one two three four and five the fifth carbon is outside the ring here it's nearest to the five from n let's look at this one so clockwise again after the oxygen molecule sorry oxygen atom one prime two prime three four and five five prime and you realize that this n is closest to the three prime n they can do the same for this and so this is a tabale or antiparallel but it still works oxygen clockwise from oxygen so one two three four five five front ends again clockwise from oxygen one two three four n so yeah that is why it's called the five prime entry prime and you might be thinking why can't we just call it up and down which one's up which one's down what are you talking about so this is a very precise chemical way of identifying direction in really and you're going to hear five prime and three prime a lot in dna replication and in transcription now because it's anti-parallel and you are now pros at um five prime and three prime zero you only need to be given one n of a dna molecule the direction of this point in order to determine what is the rest so let's look at this this is five prime if you follow the any molecule okay it goes like this and this downwards okay you know that it runs from five prime and your n should be three prime n and you know that the other string is anti-parallel so the other strand would be t prime to five prime so you only need to be given one of those four labels in order to label everything else okay so we have reached sort of the end of um the structure of dna and let me give you a quick summary before we do an uh example question and finish there are three new things you learned about dna tbn today number one the idea that it has a sugar phosphate backbone okay so this phosphate sugar phosphate sugar and phosphate sugar is helped by phosphodiester bonds now turn the dna structure has complementary base pairs complementary base pairs are when a binds to key g binds to and between a and t there are two hydrogen bonds c and g there are three hydrogen bonds these hydrogen bonds are between opposite strands okay and number three we know that the two strands of dna are anti-parallel to each other which means they run in opposite direction one is five prime three prime and the other runs from three prime to 5 prime okay knowing all that we have to do an example question um if you are watching this video now and you need to pause and i want you to think about it a little bit i think it probably wouldn't be so easy if i want to discuss it so think clearly so i'm just gonna pause awkwardly now and wait for you okay okay okay so i'm going to discuss it now i hope you actually pause the video you i'm sure you did not pause it now pause it pause it think okay let's discuss okay um let's talk about the total number of bases in the length of dna but you realize that they give you the direction of the strand which actually doesn't matter okay but they also give you a sequence but it's only a sequence of one string and we know that dna is double stranded so the total number of bases nearly of this dna is not just one two three four five six seven eight nine ten is double stranded so the total number of bases should be twenty double stranded so times two let's think about the number of purines and premaritals again dna is double stranded and complementary base pairing occurs so you have this copied from the top and this that it is a complimentary base pair of that okay so a bunch of t c binds with g now the highlighted ones appearance to count them realizing the ten of them in pyramidals they are also ten since purines always bind with pyrimidines we would expect them to be the same always always pyrimidines to pyramidance same same number ratio one to one pyramiding to purine ratio one two one and it's always like that why again appearance only bind to pyrimidines that's how complementary based pairing works so 10 parents 10 pyramidance 10 20 bases in total okay so last one is number of hydrogen bonds and dna molecule we know that here there are two hydrogen bonds between a and t and three hydrogen bonds between g and c so if we write both of them down realize that a and t we have six pairs so two times six and g and c we have four pairs it doesn't matter which trend it's on so three times four so that would be 24 you need to think a little bit but actually not that hard after you think about it so with objective questions um you got to be very very careful and have a lot of practice and that is why after every single video now you have to fill up a microsoft form a little quiz in order to make sure for me to make sure that you have watched the video and also know how to answer questions also it gives you something to do it's not your fault from this video so um i will post the quiz at the assignments section in the general channel so look there answer the quiz there once you finish this video so i hope it was helpful goodbye see you on wednesday i think if you're watching this on monday are you late don't get left behind okay if not when school reopens you'll be two chapters behind i'm getting one chapter behind look still very bad though so keep it keep on your toes ask me if anything it's a q a channel and you can also personally message me um i do reply generally quite fast so yeah see you when i see you bye