Exam Review Part B.pdf - Biol 239 Genetics Exam Review Questions PartB \u2013 answers(Part A is under Submit Quizzes and consists of some sample multiple

Exam Review Part B.pdf - Biol 239 Genetics Exam Review...

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1 Biol 239 Genetics Exam Review Questions PartB – answers (Part A is under Submit, Quizzes and consists of some sample multiple choice questions) Note: this is NOT representative of the final exam – its just some practice questions! The final exam consists of approximately 105 multiple choice questions covering approximately 20% pre-midterm material and 80% post-midterm. There are no tutorial- specific questions. The final exam format is entirely Multiple Choice. These questions are to assist you with studying only. 1. Describe the experiment that provided proof for semiconservative DNA replication. Who were the researches who did it? This one is straight out of the textbook and notes. Meselson and Stahl. 2. Draw a DNA replication fork. On your drawing, identify (1) origin of replication, (2) polarity (5' and 3' ends) of all template strands and newly synthesized strands, (3) leading and lagging strands, (4) Okazaki fragments, and (5) location of primers (6) regions of continuous and discontinuous DNA synthesis. 3 ' 3 ' 5’ 5 ' Unwinding Unwinding Origin Origin 5 ' 3 ' 3 ' 3 ' 3 ' 3 ' 5 ' 5 ' 5 ' 5 ' 5 ' Lagging Strand Lagging Strand Leading Strand Leading Strand 3 ' RNA Primers Okazaki Fragments Okazaki Fragments continuous synthesis discontinuous synthesis discontinuous synthesis continuous synthesis
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2 3. a) Draw all the elements you would expect to see in an operon encoding 2 genes. The operon is defined at the level of DNA. Remember it is only found in prokaryotes. Note* the operator (O) can be on either side of the promoter (P) b) Draw the resulting mRNA with all the needed elements. Assume this is in E. coli. c) If a frameshift mutation occurs near the 5’ end of the coding region (ORF) of gene 1, will it affect gene 2/ORF 2? Explain why/why not? No it will not affect gene 2 because both genes are independently translated from the mRNA. They are not translated as a single combined protein. d) Why don’t eukaryotes make polycistronic mRNA? Explain in molecular terms. Eukaryotes cannot read more than one ORF from a single mRNA because of the dependence for ribosome binding at the 5’ cap. The small subunit binds at the cap and then scans the mRNA until it finds the first AUG codon and translation begins and ends at the first in-frame stop codon. Then the ribosome falls off. If there is a second ORF, the ribosome will never get to it. 4. List the possible genotypes of single-mutant E. coli cells demonstrating the following phenotypes for b -galactosidase production: a) constitutive I - P + O + Z + Y + A + or I + P + O c Z + Y + A + (or I + P + O - Z + Y + A + ) b) repressive (non-inducible) I + P - O + Z + Y + A + or I + P + O + Z - Y + A + or I + P + O + Z + Y - A + or I s P + O + Z + Y + A + c) inducible must be wildtype for all genes/elements RBS consensus O P -35, -10 ribosome TAG or (TATA binding TGA or box) site TAA Stop codon ATG….. Stop codon TT AUG AUG UAG or UGA or UAA UAG or UGA or UAA ORF 1 ORF 2 RBS consensus ORF 1 ATG…. ORF 2 5’ 3’ NOTE: always label 5’ and 3’ ends SD SD SD-like sequence for prokaryotes
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3 5. What is the sequence transcribed from the DNA coding strand information shown below?
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