320_MT2__2006_answer_key

320_MT2__2006_answer_key - Midterm 2 Statistics: 11:00...

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Midterm 2 Statistics: Re-grade Policy: Re-grade is not your opportunity to haggle for points! If you feel a factual or arithmetic error was made in the grading of an examination, not on judgments about how many points an answer was awarded, you must do the following: submit a written re-grade request along with your exam to your TA within one week of the graded exam being returned to the class. Your written request must clearly explain the error made in grading. Your entire answer will be re-graded (not just the part you think deserves more credit) by the grading TA who originally graded your exam; your grade may go up or down as a result of a re-grade. If you still have questions after the re-grade, you may contact Dr. Baker. . 11:00 Class 12:00 Class Class Average (out of 100 possible pts) 81 82 Standard Deviation 15 14 High Score 100 100 Low Score 28 25
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Last Name : _____________________________First Name : ______________________ 1 Please write your last and first name on every page (total of 4 pages). Your exam will be taken apart for grading. Answers written in pencil will NOT be eligible for re-grade. BISC 320 Midterm 2 (100 pts) Oct 11, 2006 1. (10 pts) In E. coli, after initiation of DNA replication at oriC, how is immediate re- initiation of DNA synthesis prevented at the two new oriC sequences (each of the two new double stranded oriC sequences are now composed of one old strand and one new strand) in the parent bacterial cell? Answer: SeqA protein binds to hemi-methylated double stranded DNA sequences in the vicinity of the oriC regions. This prevents DnaA protein from initiating new starts at the two oriC regions. 2. (10 pts) Show by diagram how a chemical modification of one base in double stranded DNA in vivo can result in a base pair change (mutation) in a later progeny cell. (It is not necessary to show an example of a particular chemical that changes (modifies) a certain base.) Answer: A chemical first modifies a base at a site in double stranded DNA, so that now the modified base no longer base pairs at the site it occupies. The modified base, however, is
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320_MT2__2006_answer_key - Midterm 2 Statistics: 11:00...

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