Replication fork coupling

during DNA replication a DNA molecule is duplicated to generate two identical copies the correct copying of DNA is of vital importance to the cell as errors that are introduced into the DNA may lead to heritable mutations that could be deleterious to the cell or organism thus an elaborate machinery is used both to assure correct copying and to allow the process to be regulated coupling of the two DNA polymerases one for each strand allows the process of fork movement to be coordinated to understand how polymerases are coupled at a replication fork who will first show a standard representation of the replication fork in this typical representation two DNA polymerases are moving in opposite directions with one copying the leading strand of the DNA and the other copying the lagging strand to expose the single-stranded DNA at the replication fork a six membered ring shaped complex called DNA helicase first separates the parental DNA strands this separation gives the DNA polymerases the access they need to allow copying the new DNA strand is always made in the five prime to three prime direction because the replication of the two DNA strands is coupled the leading strand is copied continuously while the lagging strand is copied in short stretches called Okazaki fragments each Okazaki fragment is initiated by a primase that synthesizes a short RNA primer this primer is later elongated by DNA polymerase the single-stranded DNA between the newly made Okazaki fragments is bound by single stranded binding protein or SSB in order for the tubulin raises to move together with the helicase as the fork moves the DNA template for the lagging strand must be looped around so that both polymerases are moving in the same direction with the PLIM raises now coupled DNA replication can proceed coordinately on both leading and the lagging strand once the lagging strand polymerase reaches the RNA primer from the upstream Okazaki fragment the lagging strand loop is released and Okazaki fragment maturation pod ligation by polymerase 1 and DNA ligase occurs while this maturation is occurring the primers enzyme that is also traveling with the fork as part of the replisome this shakes a new RNA primer on the lagging strand once this primer is made the lagging strand polymerase on the replisome having completed synthesis of the previous lagging strand then re-engages from the 3 prime end of the new primer forming a new loop on the lagging strand DNA synthesis thus proceeds with the leading strand polymerase continuously engaged with the DNA and the lagging strand polymerase engaging and disengaging as each Okazaki fragment is synthesized to synthesize the lagging strand the DNA template is Luke out while it is coupled to the represent complex and the loop is released after each Okazaki fragment is completed the length of the loop DNA at his maximal sized is therefore the length of an Okazaki fragment which in bacteria is about 1,000 base pairs

Channel: Oxford Academic (Oxford University Press)

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Keywords: yt:quality=high, video, oxford university, Oxford university press, education, publishing, scholarship, oxford, oup, oup academic, Oxford academic, Molecular Biology (Field Of Study), DNA (Chemical Compound), replication, fork, coupling, lagging strand, leading strand, craig

Id: QMX7IpME7X8

Length: 3min 28sec (208 seconds)

Published: Tue Aug 12 2014