In this very quick overview of DNA replication, we're going to be talking about the various steps involved in DNA replication. Talking about the key components or enzymes that are involved in making this process happen and with this we're just going to go into a bit of understanding of why it's important to replicate DNA throughout our lifetime. So DNA replication of course is the process by which DNA is copied and multiplied within our cells before they replicate or undergo mitosis need to replicate DNA so that when they replicate every single cell that we make in our body has the necessary DNA to survive and thrive. So therefore it's important for DNA replication to be present in our system so we can say that it's importance lies in ensuring copies of our cells have the necessary genetic material. The function is as we've discussed in a prior video DNA and genetic material all of this encodes for various proteins that are going to be necessary for various functions in our body. So aside from that DNA replication also has a proofreading mechanism to ensure that mistakes and mutations are limited or not introduced but to fully understand how all of this works we have to review the structure of DNA. So again DNA have the monomer of nucleotides these are the building blocks nucleotides chained together to form a single strand of DNA so in this next part of this image this whole bit right here this is going to be one DNA strand. The DNA in our body is going to be structured in a two or a double stranded manner and this essentially means that two strands of DNA one and two right over here. We have two strands of DNA that come together to form our DNA structure and this occurs via two separate strands linking via hydrogen bonds. As you can see right here these lines in the middle those are going to be hydrogen bonds between different nucleotide bases and do note that there is a specific base pairing that's present in our DNA as you can see right here a or adenine always pairs with thymine or vice versa. And cytosine always pairs with guanine or vice versa. So here we've kind of explored the structure of DNA. Next I want us to have an understanding that in order for DNA to be replicated or in order for our body to actually work with this particular molecule. We need to rip it apart so that we can actually work with it so this double-stranded base pairing or the series of hydrogen bonds in the middle this needs to be broken apart in order for us to access the DNA and replicate it so let's talk about how that's done. So the first thing or key player that I want to introduce here is going to be helicase. Helicase is a particular enzyme that unwinds DNA so specifically it breaks apart that double stranded structure by breaking apart those hydrogen bonds. So as you can see we have this DNA structure that's double-stranded. Helicase essentially comes along to separate those double strands so we can add that to the definition separates DNA in two separate strands it separates the two into one. So now that DNA has been separated into separate strands, it's now much easier for other proteins or enzymes within the body to do what they need to do for replication. So moving on the next part that I want to introduce would be DNA polymerase. So DNA polymerase is going to be the enzyme that's responsible for replication DNA polymerase can bind onto the DNA and add new nucleotide strands so it builds new nucleotide strings. And this is going to be based off the nucleotide sequence that's found in these separate strands so for example DNA polymerase combine onto the strand at the top and what it's going to do essentially is read the nucleotide sequence. Those adenine, thymines, guanines, and cytosines. And essentially adds the opposite or the inverse set of nucleotides. So for example if this is the DNA strand that we're working with c g t a, DNA polymerase is going to read that and create a new DNA strand nucleotide by nucleotide based on what's present. So if there's a cytosine that it's reading it's going to add guanine. If there's a guanine it's going to add the opposite cytosine. Thymine again same thing the opposite and for this last one it's going to add the opposite until it gets to the very end of that DNA strand. So that's what DNA polymerase does is it builds new nucleotide strands by reading the template strands and that's what we call the pre-existing DNA that we're using. Aside from that in order for this to happen or in order to direct where DNA polymerase needs to bind to start the whole process we have another enzyme referred to as primase. Primase is the enzyme that essentially signals or DNA replication starts. So both of these work together to initiate the replication process and to build a new DNA strand. Another thing to note about here with DNA replication is that when we rip apart that double-stranded DNA we have a leading strand and a lagging strand that run opposite of one another do note that the leading strand is replicated continuously. Meaning that chain of nucleotides is just made seamlessly or continuously line by line. However for the lagging strand since it is running the opposite way it is built in a discontinuous manner, where everything is fragmented so this one is a little bit different in order for these fragments to be linked together because again DNA needs to be continuous so to bridge these gaps we do need another enzyme called ligase which is going to be an enzyme that links DNA fragments. Now the difference between leading and lagging strands again just just based on how the corresponding DNA is built. When it's continuous one is discontinuous I'm aware of that it's kind of hard to visualize this without an animation so there will be a follow-up video to this that I highly recommend you watch so that you can see how this difference occurs and why ligase is necessary to build this discontinuous strand at the bottom aside from that DNA polymerase also proofreads all of the nucleotide sequences that it makes to ensure that there are no mistakes that mutations are minimized so to end this video I have a practice question here for you so keep the case again is what separates two DNA strands from one another for replication. Go ahead and select what type of chemical bond is broken in this process is it covalent ionic hydrogen or peptide. Please pause the video and unpause once you have an answer. And if you selected hydrogen bonds that would be the correct answer