Exam 2 key fall 2010

Exam 2 key fall 2010 - Biol 221 Fall 2010 NAME_Key_ Exam 2...

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Biol 221 Fall 2010 NAME________________ Key _____________________ Exam 2 [TEAR OFF THE FIRST PAGE OF THE EXAM AND HAND IT IN WITH THE SCANTRON.] Short Answer. 25 points (5 points each). 1. Sketch a diagram depicting oxidative phosphorylation. Label the electron donor , electron acceptor , PMF and ATP Synthase . 2. Sketch a bacterial DNA replication bubble. Label the leading strand , lagging strand , 5' and 3' ends , and the oriC . 3. Sketch a ribosome translating a mRNA. Label the 5' and 3' ends and the A, P and E sites . List the steps involved in the elongation reactions . Make sure you mention which steps involve the A, P and E sites. . . NADH NAD + O 2 : H 2 O H + H + H + ADP + P i ATP PMF ATP Synthase electron donor electron acceptor 5’ 3’ 3’ 5’ 3’ 5’ 3’ 5’ 3’ 5’ 5’ 3’ oriC lagging strand lagging strand leading strand leading strand 3’ 5’ E P A 1. amino acid enters A-site 2. transpeptidation reaction makes peptide bond, moving growing protein in P-site into A-site 3. ribosome translocates toward the 3’ end of the mRNA so that the protein that was in the A-site is now in the P- site, and the A-site is ready for the next amino acid diagram +2 5’ EPA 3’ +1 steps in elongation +1 each for transpeptidation (P A site) and translocation (toward 3’ end of mRNA) diagram +3 labels +0.5 each diagram +1 antiparallel +1 leading and lagging +1 lagging discontinuous +1 ori C +1
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4. The following gene is under both positive and negative control. The positive control regulation is inducible and the negative control regulation is repressible. Show the gene when it is being expressed (is "ON"). Use a circle as the symbol for a regulatory protein and a triangle as the symbol for an environmental signal. Label all regulatory proteins and environmental signals appropriately. +1 for activator upstream and repressor downstream of promoter +1 for activator bound to DNA +1 for repressor unbound to DNA +1 for inducer bound to activator +1 for co-repressor not bound to repressor 5. Compare the life cycle of a retrovirus to that of other viruses. What are the unique steps? Is a retrovirus infection acute, chronic, latent or slow? Explain. A retrovirus binds to receptors on the target cell and is internalized by membrane fusion . It uncoats , and then replicates by reverse transcription (unique) . Its DNA then translocates to the nucleus and integrates into the host chromosome (unique) . It begins to be transcribed and translated as a polyprotein right away. The polyprotein is processed, new RNA is transcribed, and new virions are assembled and bud from the cell . After an initial set of symptoms, this replication, assembly and budding happens immediately, but slowly , and continues for several years (until the host dies). Therefore, retroviral infections are slow infections. +1 for at least two steps (binding, membrane fusion, uncoating, budding) common to other viruses, too
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Exam 2 key fall 2010 - Biol 221 Fall 2010 NAME_Key_ Exam 2...

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