{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

Notes Feb 17 - Notes Feb 17 Table 25.2 DNA polymerase alpha...

Info icon This preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
Notes Feb 17 Table 25.2 - DNA polymerase alpha o Extends 5’-3’ direction o Doesn’t have proofread exonuclease o Moderately processive o Important role is that it associates with primase (which is a RNA polymerase) o In the case of eukaryote, there is a protein complex consisting of pol alpha and a different protein subunit that is the primase that travel together on the DNA laying down a few primers either at the origin or at the lagging strand okazaki fragments o Pol alpha extends the primer with DNA a little bit with only around 15 nucleotides that get erased and that’s why it doesnt matter if there is a certain error frequency o Role of DNA pol alpha is just to get things started at the origin or at the okazaki fragment - Pol delta and epsilon divide the replication and polymerization work - It is now thought that epsilon is on the leading strand and delta is on the lagging strand - PCNA- eukayote sliding clamp o Binds to DNA pol delta and epsilon Fig 25.21 - Beginning of an okazaki fragment - Green is RNA primer - A little bit of DNA is synthesized by pol alpha extending the primer for a bit (blue extension) - Regular DNA pol (delta or epsilon) extends that RNA primer - Why does DNA polymerase alpha not need a 5’ to 3’ proofreading exonuclease? o If there are errors, RNAase H removes the RNA primer leaving 1 ribonucleotide, then some other nuclease chews that, and the part that was made by DNA pol alpha, especially if there is an error, so 1 in 10^ time there will be an error in DNA pol alpha; but the DNA coming from the other lagging fragment fills in the gap and that one is done by a pol that does have a proofreading exonuclease o Eukatyotes have this odd feature where a DNA pol alpha is used to extend primers, and while there might be a relatively high error rate, flap endonuclease will chew away the error, and then you get extension by a normal DNA pol with high processivity - Removal of RNA primers in Eukaryotes
Image of page 1

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
o RNAase H1 excises all bu tthe 5’ ribonucleotide of the RNA primer o
Image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern