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Exam 2 for Molecular Genetics - Spring 2005 | BI 381, Exams of Molecular biology

Southeast Missouri State University (SEMO)Molecular biology
Prof. Allen C. Gathman

Material Type: Exam; Professor: Gathman; Class: Molecular Genetics; Subject: Biology; University: Southeast Missouri State University; Term: Spring 2005;

Typology: Exams

Pre 2010

Uploaded on 08/08/2009

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BI 381 Exam 2 Spring 2005
Allen Gathman
Instructions:
1. Don’t relax. A recent study showed that some tension during an exam enhances
performance.
2. Genetic code and wobble tables at the end of the exam.
1. You are studying the synthesis of tryptophan in the archaebacterium Methanosarcina
mazei. You have four mutants, called trp1, trp2, trp3, and trp4. Each of these mutants is
a tryptophan auxotroph, and each has a mutation in only one gene.
a. ( 5 points) What compound could you supply in the media that would allow all of
these mutants to grow?
b. (15 points) You try growing your mutants on media with various compounds added.
Trp1 grows on minimal medium with chorismate (CHOR), indole-glycerol
phosphate (IGP), or anthranilate (ANT) added.
Trp2 grows on minimal medium with ANT or IGP added.
Trp3 grows on minimal medium with CHOR, IGP, ANT, or shikimate
(SHIK) added.
Trp4 grows on minimal medium with IGP added.
Diagram the pathway of tryptophan synthesis in this organism below, and mark the
enzymatic reaction each mutant is unable to perform.
c. (5 points) If you put trp2 cells on minimal medium, what compound(s) would
accumulate?
pf3
pf4

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Download Exam 2 for Molecular Genetics - Spring 2005 | BI 381 and more Exams Molecular biology in PDF only on Docsity!

BI 381 Exam 2 Spring 2005 Allen Gathman Instructions:

  1. Don’t relax. A recent study showed that some tension during an exam enhances performance.
  2. Genetic code and wobble tables at the end of the exam.
  3. You are studying the synthesis of tryptophan in the archaebacterium Methanosarcina mazei. You have four mutants, called trp1, trp2, trp3, and trp4. Each of these mutants is a tryptophan auxotroph, and each has a mutation in only one gene. a. ( 5 points) What compound could you supply in the media that would allow all of these mutants to grow? b. (15 points) You try growing your mutants on media with various compounds added.  Trp1 grows on minimal medium with chorismate (CHOR), indole-glycerol phosphate (IGP), or anthranilate (ANT) added.  Trp2 grows on minimal medium with ANT or IGP added.  Trp3 grows on minimal medium with CHOR, IGP, ANT, or shikimate (SHIK) added.  Trp4 grows on minimal medium with IGP added. Diagram the pathway of tryptophan synthesis in this organism below, and mark the enzymatic reaction each mutant is unable to perform. c. (5 points) If you put trp2 cells on minimal medium, what compound(s) would accumulate?
  1. (10 points) Methanosarcina mazei turns out to have a novel DNA repair mechanism that hasn’t been observed in any other organism. Some biochemical studies show that it’s started by an enzyme that hydrolyzes the phosphodiester bond immediately 5’ of the nucleotide containing an abnormal base. Do you expect this repair mechanism to be highly specific, or to work on a wide variety of lesions? Explain why.
  2. (10 points) A really weird thing about Methanosarcina mazei is that, in its mRNAs, the codon UUA is translated as phenylalanine (phe) rather than (leu). What tRNA or tRNAs is (are) different in this organism compared to most organisms, and thus cause(s) this change in coding? Explain as specifically as possible, telling both what tRNAs are in most organisms, and what’s different in Methanosarcina mazei. .
  1. (5 points each) a. What modifications occur to RNA transcripts in eukaryotes before they’re released to the cytoplasm? Just name them. b. Tell what is synthesized by each of the three eukaryotic RNA polymerases. c. Where is Streisinger slipped mispairing likely to happen, and why? d. Why are transition mutations more common than transversion mutations? e. At which end of an intron is a phosphodiester bond hydrolyzed first? f. How are pyrimidine dimers repaired in bacteria and plants?