Mutagenesis and Repair (4-0-07)

Mutagenesis and Repair (4-0-07) - mutagenesis repair...

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

View Full Document Right Arrow Icon
mutagenesis & repair 4/5/07 mutation- heritable change in DNA in prokaryotes and eukaryotes, in cells there are a lot of ways other mutations can come about other than some agent changing one nucleotide into another nucleotide. Mutations have to be copyable, still made out of nucleotides, but that’s not necessarily how that happens. Lesion- some kind of DNA damage that does not create a standard nucleotide. Instead it creates a non-standard chemical structure in DNA. It is therefore not heritable because it is not something that DNA polymerase can reproduce or incorporate into the new strand. We still talk about lesions because lesions often cause mutations. In replication, DNA polymerase comes upon the lesion in the template strand, and because the lesion does not base pair the same way as the original nucleotide would have base paired, DNAP inserts an incorrect nucleotide or an incorrect number of nucleotides in the new strand. Lesions on one strand of DNA can often cause a mutation on the other strand of DNA at replication. Lesions will not have names like insertion, deletion, transversion, etc. Spontaneous- arise out of the structure of DNA and out of the replication of DNA itself. See diagram. The covalent bond between the sugar and the base on the 1’ carbon sometimes breaks, so now it is held together by the phosphodiester bonds on 3’ and 5’ carbon. Now that base disappears, and the deoxyribose appears without a base. Chemically, both “AP sites” are the same. The only difference is what used to be there. What’s the effect? Most of the time, this does not lead to mutation. If there as an AP site on the template strand during replication, DNAP cannot pick up anything that can base pair with an AP site! The DNAP will dissociate from the template right at the AP site. It will move down the strand, re-associate with the template when there’s a new primer, and then continue. What did it left behind? A single- stranded “gap” of DNA…it’s not a deletion, so what is it? This is the usual situation. DNAP comes upon AP site, instead of dissociating, it will stay in place. In a special situation, it picks up a random nucleotide onto the 3’ end of the new strand, creating a substitution- could be either transversion or transition. Or, what
Image of page 1

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

View Full Document Right Arrow Icon
could also happen (still under special circumstances), DNAP gets to the AP site,
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