bio study 2 - Deamination of Cytosine cytosine methylation...

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

View Full Document Right Arrow Icon
•Deamination of Cytosine cytosine methylation is a contributor to mutation hotspots deamination: occasional loss of amino group of 5-methylcytosine is mutagenic because it creates normal thymine creates G-T mismatch of normal cytosine creates uracil recognized by base repair system called base excision repair uracil is recognized and repaired •Spontaneous Mutations -Byproducts of metabolism created in our cells as the result of mitochondria •Lecture Outline •Induced Mutations are are caused by exogenous (outside) sources of DNA damage •Sources of exogenous DNA damage •Chemicals –Natural •In foods, e.g. aflatoxin (fungus that grows on moldy peanuts) –Man-made/man-increased •Nitrogen Mustard - WWI nerve gas -extreme pain and extensive lung damage when inhaled •Benzopyrene - smoke from coal, autos, cigs •Ultraviolet (UV) Radiation (from sun) •Ionizing radiation –Natural: radon gas, cosmic rays –Man-made: x-rays, nuclear tests Some mutagens are chemicals that change the hydrogen bonding properties of bases •UV Radiation -mutagen in all viruses and cells -chemical changes in bases resulting from absorption of the energy from light -major products formed: Pyrimidine dimmers: covalently joined pyrimidines (primarily thymine) that are adjacent in the same polynucleotide strand -chemical linkage brings bases closer together, causing distortion of helix, which blocks transcription and translation proton hits intrasound crosslink •Fate of DNA damage •Tolerated (ignored) •Repaired •Can kill the cell or cause the cell to kill itself (senses its own danger) •Can become fixed , resulting in a mutation (Note: fixed <> repaired) •DNA damage (and DNA damaging agents) can be. .. •Cytotoxic - kills cells Mutagenic - causes mutations •Carcinogenic - causes cancer -free radicals from ionizing radiation’s reaction with water or living tissues –High correlation between muticity and carcicity •How does DNA damage kill cells? •In many ways •How does DNA damage cause mutations? •In many ways ex: when a damaged base mispairs - O6-ethyl-gaunine pairs with thymine
Background image of page 1

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

View Full DocumentRight Arrow Icon
- guanine + ethylmethanesulfate =O6-ethyl-guanine - add bulky side groups which alter base pairing or distort structure -deaminated cytosine pairs with adenine •Examples of mutation fixation •Replication of an unrepaired misincorporation - If mismatch repair fails, then when that cell goes though mitosis, one of the daughter cells still has the mismatch - If that cell then replicates its DNA before the mismatch is repaired, then the mutation becomes fixed •Replication of an unrepaired cytosine deamination (deaminated cytosine = uracil) -If that cell then replicates its DNA before the deamination is repaired, then the mutation becomes fixed.
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 06/01/2011 for the course ANTHRO BIO 2b taught by Professor Egan during the Spring '11 term at UC Irvine.

Page1 / 11

bio study 2 - Deamination of Cytosine cytosine methylation...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online