DNA Structure & Replication

by Georgina Cornwall, PhD

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    So now you know all about chromosomes and that they replicate during S phase of the cell cycle. Let us take a deeper look into what actually happens during S phase in replication of DNA. By the end of this lecture, you will be able to diagram the manner in which nucleotides assemble themselves in DNA as well as explain the implications of semiconservative replication. You will be able to describe the process of DNA replication and the role of each of the enzymes in that process as well as explain modifications that are necessary for eukaryotic chromosomes. We will begin with a quick review of DNA structure. You will recall that there are a phosphate and sugar backbone. Much like a spiral staircase, there are steps made of nitrogenous bases and these steps and nitrogenous bases with the phosphate, sugar backbone form a whole molecular DNA, which has an antiparallel orientations. That is each strand is in opposition to the other strand, so they run in an antiparallel fashion, which lends itself to some particular situations during DNA replication that need a little bit of adaptation. Looking at that antiparallel orientation, we know that there is a three prime OH group that is going to be really important to us during DNA replication and on the other strand that same end, you have a five prime phosphate hanging off. The reason this is important is DNA polymerase can only read strands from the three prime to five prime directions. It can only go if we were counting 1, 2, 3, 4, 5. It can only read the three prime to five prime. Keep that in mind. You also will recall that the nitrogenous base steps are held together with hydrogen bonds. There are two bonds between adenine and thymine...

    About the Lecture

    The lecture DNA Structure & Replication by Georgina Cornwall, PhD is from the course Understanding Genetics. It contains the following chapters:

    • The Structure of DNA and RNA
    • Prokaryotic Replication
    • Special Enzymes for Replication
    • A Closer Look on the Replisome
    • Eukaryotic Replication

    Author of lecture DNA Structure & Replication

     Georgina Cornwall, PhD

    Georgina Cornwall, PhD

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