MBIO 3410 lecture Sept 25 2007

MBIO 3410 lecture Sept 25 2007 - Outline last lecture...

Info iconThis preview shows pages 1–8. Sign up to view the full content.

View Full Document Right Arrow Icon
1 Outline last lecture Transcription in eukaryotes Promoters RNA polymerase II RNA polymerase subunits • CTD of RNA polymerase II RNA polymerase II transcription factors • TFIID TBP • TFIIA TFIIB and RNA polymerase binding TFIIE, TFIIH and TFIIJ factors • phosphorylation of the carboxyl- terminal domain (CTD) Activation of RNA polymerase II Chromatin-modifying complexes Chromatin remodeling complexes Transcription process Eukaryote transcriptional termination Processing prokaryote mRNA mRNA processing in eukaryotes mRNA transcript cleavage and polyadenylation mRNA splicing Spliceosomes Alternative mRNA processing Alternative splicing Mutagenesis Mutations DNA replication fidelity
Background image of page 1

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

View Full DocumentRight Arrow Icon
2 Physical Mutagens Absorption of high-energy ionizing radiation (X-rays and γ- rays) causes some molecules to lose electrons These electrons can lead to chemical alterations in DNA Strand breaks, base and/or sugar destruction Non-ionizing radiation causes molecular vibrations or promotion of electrons to higher energy levels Formation of new chemical bonds UV light produces pyrimidine dimers
Background image of page 2
3 Base analogs = derivatives of bases with altered base pairing properties that can cause direct mutagenesis Chemicals can react with DNA and alter its properties Nitrous acid deaminates cytosine to produce uracil This base pairs with adenine and causes G-C→A-T transitions hypoxanthine results in A-T→G-C transitions Alkylating and arylating agents produce lesions Intercalators result in insertion and deletion mutations Most chemical mutagens are carcinogens Chemical mutagens
Background image of page 3

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

View Full DocumentRight Arrow Icon
4 DNA damage DNA lesions = alteration to the normal chemical or physical structure of DNA Chemicals and radiation can alter the bases leading to loss or alteration of base pairing that could become fixed in the DNA by direct or indirect mutagenesis This chemical change may also lead to a physical distortion in the DNA, blocking replication and/or transcription (cell death) Depurination = spontaneous cleavage of the N- glycosylic bond (N-9 of the purine bases and C-1’ of the deoxyribose sugar) leads to loss of the base from DNA Apurinic site is a non-coding lesion (occurs at a rate of 10,000 purines lost/human cell/hour! Depyrimidination can also occur
Background image of page 4
5 Oxidative damage Occurs under normal conditions due to reactive oxygen species (ROS) in all aerobic cells Superoxide Hydrogen peroxide Hydroxyl radical (•OH) = can attack DNA at many points
Background image of page 5

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

View Full DocumentRight Arrow Icon
6 Alkylation Electrophilic chemicals that add alkyl (methyl) groups to nucleic acids Some of these lesions are potentially lethal as they interfere with unwinding of DNA (replication and transcription)
Background image of page 6
7 Bulky adducts Cyclobutane pyrimidine dimers are formed by ultraviolet light Cyclization of the double bonded C5 and C6 carbon atoms of each base Leads to loss of base pairing with opposite strand, local denaturation of the DNA, and the bulky lesion disrupts DNA replication and transcription
Background image of page 7

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

View Full DocumentRight Arrow Icon
Image of page 8
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 31

MBIO 3410 lecture Sept 25 2007 - Outline last lecture...

This preview shows document pages 1 - 8. Sign up to view the full document.

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