ex_3A_2009answers - BMB/Micrb 460 / Exam 3 / TEST FORM A/...

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BMB/Micrb 460 / Exam 3 / TEST FORM A/ April 8, 2009 NAME: 1 QUESTIONS ARE WORTH 4 POINTS UNLESS NOTED OTHERWISE Questions 1 to 3: (2 pts) Inhibiting the function of wee1 kinase in yeast would (circle one) INHIBIT normal / PROMOTE abnormal progression of the cell cycle. (Note – the name of the gene is a clue) (1 pt) The primary target of wee1 is__________ MPF or cdk1 or cdc2 _________________ (3 pts) Describe (or draw) in more detail how this target is regulated by phosphorylation and dephosphorylation. MPF receives an inhibitory phosphorylation from wee1 MPF also receives a required stimulatory phosphorylation from CAK The inhibitory phosphorylation is removed by cdc25 When cyclin B/ cdk1 levels are first rising, the wee1 inhibitory phosphorylation overwhelms the cdc25 dephosphorylation. However, once levels rise high enough, a small amount of MPF becomes active. MPF then downregulateds wee1 and upregulates cdc25 so that all MPF is rapidly activated. (2 pts) Rb INHIBITS / PROMOTES (circle one) cell cycle progression. (1 pt) The primary target of Rb is _____ E2F _____________. (3 pts) Describe (or draw) in more detail how Rb is regulated and its effect on its target. Rb binds and inhibits E2F activity G1 cyclin (D) /cdks phosphorylate Rb Phosphorylated Rb cannot bind E2F, E2F is then released E2F is a transcription factor that activates transcription of G1-S phase cyclones (Cyclin E) Cyclin E also phosphoryates Rb, leading to release of even more E2F and E2F stimulates transcription of other genes required for S phase
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BMB/Micrb 460 / Exam 3 / TEST FORM A/ April 8, 2009 NAME: 2 4. An asynchronous culture of mammalian cells was treated with a new drug and then analyzed for DNA content using a fluorescence-activated cell sorter (FACS) after 24 hours (graph below). Which of the following conclusions are consistent with this data? a. The drug arrests cells in G 0 b. The drug arrests cells in G 1 c. The drug arrests cells in S d. The drug arrests cells in G 2 e. The drug has no effect on cell proliferation f. The drug causes apoptosis 5. Fig 2a (right) is a Southern blot performed by Lee and Nurse on wild-type (wt) yeast or yeast containing the human Cdc2 homologue instead of the yeast cdc2 gene ( Δ ). One implication of the data is that the yeast and human cdc2 genes do not have similar nucleic acid sequences. Suppose the human and yeast genes did have similar nucleic acid sequences. Which of the results below would you expect? A 6. Cyclin protein levels oscillate during the cell cycle. The primary mechanism for increasing cyclin levels is a. blockage of ubiquitin-mediated targeting for degradation b. dephosphorylation of inhibitory phosphorylations c. activation of transcription d. stimulation of translation Fig. 2a.- Southern blot of BamHI- digested DNA from a wild-type yeast strain (wt – lanes 2 and 4) or the cdc2Sp deletion strain containing a rescuing human
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This note was uploaded on 10/19/2009 for the course B M B 460 taught by Professor Hanna-rose,w during the Spring '08 term at Pennsylvania State University, University Park.

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ex_3A_2009answers - BMB/Micrb 460 / Exam 3 / TEST FORM A/...

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