DNA Replication Made Easy

in this video we will study about the DNA replication DNA replication is the biological process of producing two identical replicas of the DNA from one original DNA molecule and as simple as it may seem it is one of the most complicated biological processes and involves the accurate copying of almost 6.5 billion base pairs in a complete set of DNA during each cell division DNA replication takes place inside the nucleus of the cell there are two identical and new copies of the DNA are synthesized from the original DNA the newly formed set of DNA will then be transferred to the future' nucleus that is produced during the process of cell division at the end of cell division we have two completely new cells each having its own set of DNA and the previous videos in this section we discussed in detail about the structure and function of the DNA about nucleic acids and we also talked about the concepts of complementary base pairing and directionality these concepts are essential for understanding the process of DNA replication so make sure to watch both these videos for a better understanding of this section now let's talk about the overview of the process of DNA replication what you see here is the simple double helix model of the DNA in this model you can note that it consists of these two blue lines which basically represent the sugar phosphate backbones of the DNA and at the center we have these orange lines which represent the nitrogenous base pairs of the DNA if we untwist this double helix model we will get something which is known as the stepladder model of the DNA which is a simple depiction of the structure of the DNA in this example you can see that the DNA consists of these two identical strands which almost run parallel to each other now in the process of DNA replication what happens is that these two strands separate the original DNA which separates to form these two strands is called the parent DNA and then these two strands which are separated from each other act as templates upon which new strands are copied and formed now this process is made possible by the concept of complementary base pairing basically we discussed the process of complementary base pairing in detail in the previous videos and in a nutshell you can note that the DNA consists of four nucleobases which are the adenine cytosine guanine and thymine in the structure of the DNA the base adenine always pairs with the base thymine and the base guanine always pairs with the base cytosine this is called the chargaff's rule of DNA complementary base pairing this is done so to maintain a proper distance between the two strands and also maintains a proper stable structure of the DNA helix when the parent DNA split each strand acts as a template for the formation of new strand this leads to formation of two completely new sets of DNA which are called as the daughter DNA now if you take a closer look at this step ladder model of the DNA you can note that it consists of these two strands which are joined together in the center by hydrogen bonds now these two strands run in completely opposite direction to each other which means they are anti parallel and they also have a direction now in DNA we don't have the north south east or west directions but on DNA we have two ends a five prime end and a three prime end of this strand and since the strand above is running in completely opposite direction it will have its 3 prime end on this side and its 5 prime end on this side so due to this the strand below is said to be running from the 5 prime to 3 prime direction and the Strand above is said to be running from the 3 prime to 5 prime direction now to understand the concept of direction in DNA in a better way let's take a brief and close look at the structure of the DNA now in this example you can see the different nucleotides and how they are joined together in and DNA if we take one nucleotide out from this strand you can see the simple depiction of the chemical structure of a nucleotide we will not go into the details as we have discussed the structure in detail in previous videos but you can note that we have three important groups in a nucleotide which are the phosphate the sugar and the nitrogenous base now if we isolate the deoxyribose sugar from this nucleotide we can see that the carbon atoms in the deoxyribose sugar are numbered from 1 to 5 in a clockwise manner with a fifth carbon outside the ring now you can compare this illustration with a chemical structure of deoxyribose for a better clarification and it is the fifth carbon to which the phosphate group is always attached now if you take a look at the structuralist raishin of a single strand of DNA again you can note how the deoxyribose sugars are arranged in this single strand and you can also see how all the deoxyribose sugars are aligned in this direction due to this orientation the fifth carbon is always located on this side to which the phosphate groups are attached and the third carbon are always located on the this side to which the hydroxyl group is attached this defines the five prime end and the three prime end of this strand of the DNA now if you take a look at the second strand of the DNA you can note the key difference that is that it runs in completely opposite direction which you can clearly tell by looking at the orientation of the sugar molecules in this strand these sugar molecules are aligned in this direction which is completely opposite to the strand below and this defines the three prime end and the five prime end of this strand now the question arises why is the conservative direction important in DNA replication well this is because the main enzyme of the DNA replication which is DNA polymerase it can only add new nucleotides as a three prime end of the DNA this means that the process of DNA replication can only progress from the five prime end to the three prime end of the DNA this is because the new nucleotides can only be added at the three prime end well we will get into the details of the concept of direction in DNA replication later in this video now let's talk about the various enzymes that make this complex process of DNA replication possible in this table we will study about the name the symbol and the function of the enzyme involved in the process of DNA replication the first enzyme that we will discuss is the enzyme helicase which will be denoted by this symbol the main job of the enzyme helicase is that it unzips the double helix structure of the DNA the enzyme helicase performs this function by breaking the hydrogen bonds between the base pairs this separates these two strands creating the replication fork upon which various other enzymes will add in the process of DNA replication so the next enzyme we will discuss is the enzyme DNA polymerase which will be denoted by this symbol the DNA polymerase performs the vital function of formation of a new strand of DNA known as the daughter strand now in this example you can see the replication fork created by the enzyme helicase and here is the five prime end on the left and the 3 prime end on the right of the upper part of the DNA the DNA polymerase performs a function of formation of a new strand by arranging new nucleotides in the form of a DNA strand by using the parent DNA as a template now you can also note that the DNA polymerase cannot synthesize a brand new strand but requires a small sequence of RNA to do so this action is performed by another enzyme the next enzyme which we will discuss is the enzyme RNA primase the RNA primase will be denoted by this symbol like we just discussed the DNA polymerase cannot initiate the synthesis of a new strand of DNA from scratch so the enzyme Primus synthesizes a short segment of RNA known as the primer which acts as a guide for the DNA polymerase to synthesize the strand further now this short segment of primer is later removed and replaced by a new segment of DNA the next enzyme we will talk about is the DNA ligase which will be represented by this symbol in the process the DNA ligase performs a vital function of joining together of the Okazaki fragments on the lagging strand now this may seem complex right now but we will get to this in detail later in this video and the final enzyme we will talk about is the enzyme topoisomerase which will be denoted by this symbol the DNA is a double helical structure which consists of two strands of DNA which are twisted around each other when the enzyme helicase opens up the DNA there is generation of stress in DNA strands which can lead to supercoiling of DNA now this process is solved by topoisomerase which cut and resealed the fragments of DNA to relieve the stress that is produced by unzipping of the DNA so this was part one of this video in which we discussed the overview the concepts of directionality and the various replication enzymes involved in the process of DNA replication in part 2 of this video we will study about the actual replication process thank you so much guys for watching this video make sure to subscribe us on youtube for all the latest videos and also make sure to like our page on facebook for all the latest updates and flashcards you can also follow us on instagram for all the latest flashcards

Channel: MEDSimplified

Views: 962,904

Keywords: njaeeb, video, animation, lesson, tutorial, anatomy, zone, kenhub, strong, medicine, dna, replication, transcription, translation, CELL, BIOLOGY, DNA RNA, DNA CRASH COURSE, prokaryotes, eukaryotes, hindi, repair, report, khan, gyrase, ligase, dna replication, dna replication animation, dna replication amoeba sisters, dna replication transcription translation, biology 101, biology cell structure, krebs cycle

Id: ePZc-71PT_4

Length: 9min 15sec (555 seconds)

Published: Mon Dec 18 2017