answerkeyquiz_7topost - depends on how well they explain...

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Question 1. Correct answer : (5 pts.) cAMP. Also acceptable is lactose and CAP Question 2. Correct answers: (5pts) The ribosome binding site in front of the β subunit is much stronger than the one in front of the α subunit thus much more β gets synthesized. Also acceptable is that the α subunit gets degraded faster than the β subunit. Other answers : (various pts) (5pts) The secondary structure of the mRNA is such that there are more/stronger binding sites for the ribosome (4pts ) A number of students said that the ribosome binding site is stronger for β than α so “transcription” is more efficient. I think this was just a minor mistake (3-5pts) There is some repressor that binds in front of the mRNA α subunit so that it’s translation is inhibited. Some try to relate this to the lac operon in that there is a repressor protein in front of the α subunit and not the β and that there is a signal that is required to remove the repressor protein to get the a subunit made. The number of points awarded
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Unformatted text preview: depends on how well they explain it. (3pts) The lifespan of the mRNA is short so translation of the β subunit occurs but the mRNA starts degrading before enough α can be made (2pts) The difference can be explained because the toxin is in a 1:5 ratio so the function of β is much more necessary than the function of α (2pts) The ratio of the subunits is 1:5 because it takes 5 β subunits and 1 α to create the toxin (2pts) A combination of mentioning that β has more active binding sites and this somehow relates to the secondary strucure of mRNA and more/less activity. They fail to mention if they are talking about transcription/translation and if they mean ribosome binding sites. (0pt) Focusing primarily on trancription of the lac operon and how it relates to cholera in a way I can’t understand. . Some also say that the β subunit IS lacI and the α IS lacy. I don’t know what they are getting at...
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This note was uploaded on 12/06/2009 for the course BIO 172 taught by Professor Clark during the Spring '08 term at University of Michigan.

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answerkeyquiz_7topost - depends on how well they explain...

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