Structure of DNA and RNA

0:08 good day students you welcome to another video lectures today we are going to be discussing about structure and function of DNA and RNA so we will be discussing under this topic under this lectures DNA will uh make a quick reev revision on DNA RNA and also we are going to discuss about the their structure and also we will talk about the the proteins because these molecules are uh DNA uh genetic carriers of genetic uh information whereby the all processes

0:56 produces uh protein and these proteins are very vital for the proper functioning of the body so DNA RNA and proteins are what we call the molecules of life so let's make a quick review DNA is stands for deoxy nucleic acid is the blueprint for life and DNA molecule is we already know that it's a molecule of life and our body is made up of

1:43 trillions trillions of cells and each of these cells contain 46 chromosomes in humans see you can see human has 23 pairs of chromosomes inside each cell and when you open this the DNA that is contained in the cell is about 2 m in length and there are 3 billion DNA sub units bases the bases are which are atcg 3 billion DNA sub units and approximately

2:30 30,000 genes and these genes are the segments of the DNA that calls for proteins functional products which are proteins that perform most of the live processes so if we look at this diagram it's trying to tell us that this is a cell and in the cell we have the nucleus and uh each uh of these nuclear nucleus of each cell there is genetic materials which is the the DNA and inside this DNA

3:19 we have what we call the the the chromosom so um sorry inside each cell we have what we call the the DNA molecules but we have already known that our cells are made up of 23 pairs of chromosomes so inside each of the cell we have the chromosomes and in the chromosomes that is where you find the the DNA so when you have this DNA and they have this letters which are thec the bases

4:06 atcg and the transcription there is a segment of this DNA that is called the gene and when this Gene is transcribed and translated it gives you a protein which carries out the function of life processes in the cell so we are going to see uh those details in subsequent slides so the DNA structure DNA is a pol nucleotide in that it's is made up of nucleotide subunits and this nucleotide each of these nucleotide consists of three components we have the

4:52 five carbon sugar which is ribos or the oxy ribos in the case of DNA we have the oxy ribos and case of RNA we have the ribos sugar and phosphate group and we also third component is the nitrogeneous base so structurally this is we have the basic nucleotide structure which has a nucle nitrogen based phosphate group and a five carbon sugar and this is uh how it looks like so we have four bases that are found in the DNA we are talking about about the the and different kinds of uh nitrogenous bases that are found in the DNA and this purine we have what

5:41 we call purine bases and we also have what we call the pamine bases so the four U uh bases that are found in DNA we have the adenine guanine which as the which are called the purine bases and we have the pyramidan bases which are the cyto and thamin so DNA is is complementary in the sense that there is complementary base pairing where adenine pairs with thine and it's be two hydrogen bonds a pairs with t we are two hydrogen bonds and cytoc pairs with quanin we are three hydrogen bond so uh the stronger

6:27 hydrogen bond is seen is in the nucleotide paing CG because it has three hydrogen bonds so this is um how they appear in the DNA molecule you have your phosphate group here this are the phosphate group have the ribos or Theos sugar you have your nitrogenous bases and a PA with t we are two hydrogen bonds G PA with C we are hydrogen bond and so on and so forth and it is uh when the one strand is going in five Prime three prime Direction the other Str will go in three prime five Prime Direction opposite direction so

7:15 the DNA structure uh still discussing and we know that the DNA is a double helical structure it has a dou helical structure in the sense that it's uh this was uh it's have this nucleotides and the uh the twisting can be either right-handed twisting or left handed twisting so we are going to see all this in details in our subsequent classes so it was first discovered by Wason and Creek you remember in our previous classes we have already discussed that so let's look at now the replication

8:03 processes that occur so when we say DNA uh DNA replication the process occurs in the nucleus because nucleus houses the DNA so in molecular biology or biochemistry when we say d application is the biological Pro process of producing two identical copies of the DNA from one original DNA molecules so it's a biological process that produces two copies of DNA that are

8:49 exactly identical from only one molecule of the DNA so the parent DNA will now give rise to two uh molecule of the DNA it's a process that occurs in all living organisms and it is the essential uh part the most essential part of biological inheritance this is how organisms uh get uh information from their inherit information from their their parent so it's essential enduring cell division and growth and also in repair and image of tissues and it is a process that ensures each

9:36 cell receive identical copy of the DNA so DNA replication processes occur in stages in the first stage we have an enzyme that is called the DNA Topo isomer DNA Topo isomer is the for uh is the first enzyme that act on the DNA molecule during replication so what does the DNA to

10:25 isomer do to the DNA it entangles the coils that is in the DNA so the next enzyme is the enzyme that is called the helicus and the helicase unzip the uh the DNA molecule whereby it exposes the strands of the nitrogenous bases for the process of the uh replication to take place so in that when that happens you have the DNA being

11:12 separated into [Music] two strands you have what two strands that are being produced so now another then the the enzyme DNA polymerus pairs the basis where it pairs a with T and G with c and the DNA polymerus also carries out the functions of checking and correcting mistakes that may have occurred during the the polymerization during the addition of the uh bases so we have three enzymes we have the DNA top isomes

12:00 which untangles the DNA coils now opening on winding the or untangling the coils because the DNA is super coil so it's now uh un coil it un Tangles it then second enzyme is the helicus which unwind The Strand to form to form two strand it unwind the unwind the double strand to form a two single strand now next one because the base P basis has been exposed so now DNA polymer the enzy will now come and act the addition of a to t g to C and also

12:45 it checks where there is mistakes that is profing check correct the mistakes so nucleotides are are now paed and then the third en the fourth enzyme is DNA lias which follows behind and bonds the nucleotides together so now lias now the two strand of the DNA are now created by by by the lies now DNA replication is a process the process is fast and accurate and error occurs in only about one of a billion nucleotides so in about billions of nucleotide that has been added

13:32 mistakes or error can occur in in one so and the process is kind of very accurate so replication begins at a specific sites that are called origins of replication origin of replication are where where replic ation starts that's where the replication uh begins okay and and and the copying of the uh DNA proceeds outward in both Direction

14:21 creating what we call uh replication Bubbles and the parent DNA strand open up as a DOTA strand grows on both side of each bubble so a eukariotic DNA molecule has many uh many Origins where application can be initiated at the same time and this is a kind of Advantage whereby it shorten a total time to copy all the the DNA So eventually all the bubbles are marged and then the end product which is the double two double stranded DNA molecules each with one new and one old strand is being

15:08 produced so then application occurs before a cell divides know the process of cell division so before cell division occurs L replication occurs to have the genetic material being shared so ensuring that each cells in a multicellular organism all carry the same genetic information it is also mechanism for producing DNA copies that Offspring inherits from parents ding reproduction the resulting double stranded DNA molecules are identical they are exactly the same so proof reading and eror checking mechanism exist in during the

15:55 replication because of that enzyme DNA polymer so it has this ability to check and correct errors what we call profing and error checking mechanism so for RNA structure and synthesis RNA is ribonucleic acid and urasil replace thamin urasil is found in DNA while thamin is found in RNA instead of thamin it's only in DNA that will see thamin so in place of timing in RNA we are going to see urin is very similar to DNA repeating subunits and also uh nucleotides the differences between RNA

16:42 and DNA uh there are some notable differences between uh DNA uh and RNA face of which is from the uh theios sugar okay the ribos the five carbon sugar that is found in RNA is it's it has what is ribos sugar so while in DNA it is the oxy ribos sugar okay so and in terms of the structure we can see DNA is double

17:29 stranded molecule forming a double helix and it uses nitrogenous babes are adenine guanine cyto and thine and base pairing occurs between adenine and tamine then cyto and guanine while in RNA it's a single stranded molecule and it contains ribos sugar as we said it uses nitrogen bases adenine cyto and uracil so in terms of pairing a PA with adinin pairs with uril and cyto pairs with guanin in terms of function functions we can see uh DNA

18:16 function in storing and transmitting genetic information and it is primarily found in the nucleus of cells and replication takes place to ensure genetic continuity during cell division while in terms of functions RNA plays various roles in protein uh synthesis and regulation of gene expression and it can be found in the nucleos and also in the cytoplasm of the cells and it include it has different types such as messenger R Transfer RNA ribosomal RNA and RNA molecules can be transcribed from DNA so

19:03 from DNA you can produce RNA molecule a process that we call transcription so these are all differences and we are going to see the process of this transcription in terms of stability now the differences between DNA and RNA DNA is more stable than RNA because DNA is double stranded molecule and it has uh the chemical properties of the oxy Rios while RNA is less stable than DNA because it is susceptible to uh degradation because of heat so we have uh we have already discussed all this and uh yeah so now we talk about

19:52 the central uh central dogma so the central dogma of molecular biology uh tends to explain the flow of information flow of genetic information that starts from DNA okay through RNA and eventually to produce protein so in all process we talk about uh transcription we talk about

20:37 um transcription right and we are going to talk about trans translation so transcription when you have DNA DNA being converted to RNA you remember we explained the process of the process of producing DNA from DNA and when that happens we can say that is called replication so DNA to DNA is

21:23 called replication while from DNA to produce RNA is transcription and when DNA is transcribed to produce RNA when RNA is translated to produce what protein that is how the flow of information the genetic information in central dogma molecular biology of course so three different RNA molecules are involved in protein synthesis three different Arna molecules we have the messenger molecule we have the which is abated as Mna we have the transer RNA TNA and we have the ribosomal

22:09 RNA okay these are the three different RNA molecules that are involved in protein synthesis and all of which have different functions which we are going to be discussing so in protein synthesis the first step is transcription which occurs in the nucleus okay and transcription is we have seen it that DNA is being converted to RNA through the process of transcription so that occurs in the nucleus in the second step we have translation where the RNA is converted to protein and this process occurs in the in the nucleus so

22:58 synthesis span nucleus it joins nucleus to the cytoplasm and we have genetic materials starting materials in the nucleus and the end product which is protein is now in the cytoplasm so it means there has to be a kind of Transportation of the information or rather of the molecules from the nucleus to the cytoplasm so now the transcription is when DNA is converted to RNA and it occurs in the nucleus first DNA is unwind in a section and then next step is Messenger AR uh

23:46 formed by bpin now with the parent strand of DNA it begins the transcription now then messenger RNA carries the message about what type of protein to to be produced from the DNA in the nucleus to the ribosomes we have known function of ribosomes as as organal so now transcription OCC Course once messenger is forms the enzymes in the nucleus remove what we call the introns and the introns are the non cording section segment of the D and then leave the exons which are the

24:32 good ones that collect that that Cod for uh for functional uh proteins products rather so now we have this uh uh process explained here okay you have your molecule consists of both the Inon junks and everything exons okay now transcription OCC course okay whereby you have initial transcript okay and then you have what we call messenger being processed where you have in the poly being attached okay and then when that happens the inance the

25:19 non-coding segment are being removed so that you only have the Exon which are the coding at the end of the matured uh M so the gentic Cod now so how is the information from uh from the messenger now being is getting converted to to the to the uh to the protein so we have what we call genetic

26:04 cing or rather genetic uh genetic code so uh genetic code is the instruction that cell uses to translate DNA into any molecule uh it is made up of cordons which are three L sequence of nucleotides that correspond to a particular amino acid that is going to be found in the protein that is going to be produced so each three consecutive bases on the messenger

26:51 is is a Cod word that is codon and it specifies an amino acid okay and the genetic code consists of 64 Hons but only 61 cords for uh for amino acid while the three cords act as signals to to either stop the process okay which one coding Aug cods for meion and it's also the start signal for for translation so and if you look at the characteristic of this genetic code it

27:36 is a triplet Cod that is the genetic code is made up of Tri plates of uh of nucleotide and it is non ambiguous it means each cordant specifies a single amino acid it is degenerates also multiple cordons can code for the same amino acid that is what we mean by degenerate it is a triplicate triplate called nonambiguous degenerate and also it is non overlapping meaning that each ribonucleotide in messenger is part of only one triplate so and it's also Universal which means almost every species on

28:23 Earth uses the same genetic code so these are the five basic characteristics of this genetic code number one is the triplet code two is nonambiguous three is degenerate four is non overlapping and five is that they are Universal so for the start and the stop cordons the start codon is a UG and it initiates the process of what protein translation and it calls for methionine while the STP cordons you remember we say there are 64 cordons and only 61 C

29:09 Amo acid while the three stop signals to stop the process or to start the process for the stopping of the process it CS Aug are the qus and it CS for methionine and meing is a is an amino acid that shows the what that translation to begin okay while this top cordon when this Cordon occurs it means that this translation should be stopped so whenever is being uh translated you when you encounter this codes it means the process will be stopped and this Cod stop cord include u a a u g a and u a g

29:57 number one is UAA number two is U number three is u a they terminate the process of protein uh translation okay or synthesis so this is how the uh the genetic code looks like okay and you have your you are cing and different amino acid that are being uh produced from that so in the second step is what we call translation where the RNA is being converted to protein

30:44 translation is synthesizing a cord from amino acid according to the sequences of the nucleotides in the in the messenger and it occurs at the ribosome in the cyto PLM of the cell and we have what we call ribosomal RNA and is which is needed for protein synthesis it helps to bind to the ribosomes and we have what we call transpar RNA which brings specific amino acid to the ribosome to be assembled as protein so we have seen the function of messenger function of ribosomal RNA and the function of the transfer RNA

31:29 so the translation we have the messenger R and when it enters we have um the small subunit and also the large subunit and you have your polypeptide being uh produced so ribozymes are the sides of what protein synthesis and it transfer R molecule looks uh it transports molecules that carries uh specific amino acids to the ribosomes for

32:15 assembly uh of the protein that is going to be synthesized or produced and each of the transpar recognizes the corre the correct Cordon on the messenger R molecule so structurally this is how it uh looks like so now the process of translation you have your free now free transfer uh free transfer with the specific Cod that I was going to be

33:02 used to be producing the amino acids okay and you have your different amino acids that are being produce from each of these uh each each each of this each of this quot and you have your amino acid being synthesized okay and the protein get buildt off from the different amino acids that are added so the steps in the uh translation process summarizes as follow number one is

33:50 Messenger leaves the nucleus and migrates to the ribosomes as the first step then the second step is Messenger bind to small ribosomal subunits then transfer brings amino acid to the ribosomes where anticodon on the transfer binds to The Cordon of the messenger RNA and the amino acid bouns to it adjoining amino acid to form a growing eptide molec similar to the structure that we just see now and transp AR without the Amo acid is released from

34:37 the ribosome then other transfer is bring amino acid to the ribosome to complete the protein molecule so this is the O idea behind the protein translation okay you have your messenger AR here and Bounds to the ribosomes you have your transfer okay and you have your transpar adding uh the the molecules of amino acid and then the growing polypeptide the growing peptide continues for the synthesis of the

35:25 protein molecule so the process of the protein synthesis it occurs in the cytoplasm okay the protein OCC course in what in the cytoplasm so that is where translation occurs and you have your ribosomes attached okay okay okay to the uh messenger RNA now you have your proteins and then you have your polypeptides this is single protein and you have your this is the peptide and you have many of the peptides that are

36:11 produced depending on which protein is going to be produced and you have your polypeptide so in summary uh the protein synthesis occurs as follow where you have messenger RNA for first is DNA molecules being uh replicated okay now now you have DNA been transcribed to Messenger to RNA right you have your DNA producing messenger RNA okay in the nucleus and after that the messenger is going to be what uh transported and it's going to be bound

36:57 to the ribosomes now the second step is Transfer RNA binds amino acids and then bring them for the amino acid to be bed to the ribosome then you have your growing peptide chain okay and then that keeps on going until you have your completed po peptide chain so both DNA and RNA have a Direction one end is the three prime and the other end is the pine end and then the cordons are read in One Direction

37:43 only there is redundancy in the genetic cot means different sequences can specify for the same Amo acids now for the mutation when there is changes there are changes in the nucleotide sequence of the DNA we said mutation occur and it can be passed from uh from one generation to the Next Generation to future generation

38:29 so we have different types of mutation we have the single base substitution which we call uh point mutation is a single base substitution for example when we said assuming this is our genetic code in sentence that reads the cut so the rat okay the cut so the rat and now there is a single substitution of the nucleotide instead of R here it it is replaced with h it is substituted with h so now the sentence will read the card so the heart so it means the entire

39:14 sentence changes the meaning it does how mutation changes the information that is carried in the DNA okay so you see how the leros mutation can be so there is also deletion where a small DNA segment is lost there is also an insertion where a segment of DNA is added there is also what we call frame shift mutation which is modification of the reading frame after a deletion or insertion resulting in all Cordon uh down steing being different there are also IM mutations that are called silent mutation okay silent in the sense that a

40:03 change of that nucleotide sequence did not necessarily bring a change in the resulting amino acid so that is a silent mutation so we have what we call somatic mutation uh it occurs in the body cells or cells that do not lead to the production of garet so somatic mutation that occurs in leave roots or stems are usually not pass onto the future generation so um that's all that's why we are going to stop I hope you really enjoyed this lecture if you are yet to subscribe to

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