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Unformatted text preview: Lauren Taranow (lmt827) Section 48950 Problems and Questions for Chapter 11 Material From Brooker pages 294-297, (3 rd edition, pages 293-296) Read and consider (but do not submit answers for) question S3. Answer questions C9, C15a, C16a-c, C21, C26, C29, E8, and the additional questions below. C9. List and briefly describe the two types of sequences within bacterial origins of replication that are functionally important and that we discussed in lecture. DnaA binding site – site on DNA to which DnaA protein binds. DnaA proteins will bind to each other, bending the DNA and causing unwinding at the adjacent AT-rich region. AT-rich region- many A/T nucleotides held together by 2 H-bonds and are easier to break. DNA begins unwinding here to form an opening. C15A. The ability of DNA polymerase to digest a DNA strand from one end is called its exonuclease activity. Exonuclease activity is used to digest RNA primers and also to proofread a newly made DNA strand. Note: DNA polymerase I does not change direction while it is removing an RNA primer and synthesizing new DNA. It does change direction during proofreading. In which direction, 5 ′ to 3 ′ or 3 ′ to 5 ′ , is the exonuclease activity occurring during the removal of RNA primers and during the proofreading and removal of mistakes following DNA replication? RNA primers are digested by exonucleases in the 5’ 3’ direction, while proofreading is performed through 3’ 5’ exonuclease activity. C16. In the following drawing, the top strand is the template DNA and the bottom strand shows the lagging strand prior to the action of DNA polymerase I. The lagging strand contains three Okazaki fragments. The RNA primers have not yet been removed. The top strand is the template DNA 3'———————————————————————————————————5' 5'***********——————*************—————************——————3' RNA primer ↑ RNA primer ↑ RNA primer |————————————||———————————||————————————| Left Okazaki fragment Middle Okazaki fragment Right Okazaki fragment A. Which Okazaki fragment was made first, the one on the left or the one on the right?...
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- Fall '08