Review Session 9 11 25 Homework Problems Practice problems are required but ungraded You are expected to complete these practice problems prior to 7pm Thursday when the review session starts This weeks review session is at 7pm Thursday 9 11 25 in Mahar Auditorium If you test proteins involved in regulating the metaphase to anaphase transition in normal cells what would you conclude about the stage of the cell cycle from the following observations A The cell is in metaphase B The cell is in anaphase C The cell could be in either metaphase or anaphase 1 MAD is binding to CDC20 2 Cohesin is binding sister chromatids together 3 Securin is missing from the cell 4 Separase is present in the cell 5 MAD is not binding to CDC20 6 APC is not binding to CDC20 Mutations can occur that a ect proteins regulating the metaphase to anaphase transition What could result from the following mutations A The cell goes into premature anaphase B The cell is stuck in metaphase C The cell completes mitosis normally 1 A gain of function mutation that causes kinetochores to release the unattached signal even when they are attached to spindle bers 2 A loss of function mutation that prevents MAD from changing shape when the unattached kinetochore signal is lost 3 A gain of function mutation in CDC20 that produces much more protein that normal 4 A loss of function mutation in Securin that prevents it from binding Separase 5 A loss of function mutation in Securin that prevents it from binding Ubiquitin Which of the following could result in a cell getting stuck in metaphase 1 Gain of function mutations in APC that increase its concentration in the cell 2 Loss of function mutations in Securin that prevent its binding to ubiquitin 3 Loss of function mutations in APC that prevent any APC protein from being formed 4 Loss of function mutations in Cohesin that prevent its degradation by Separase A cell has moved to anaphase even though some kinetochores are not yet attached to spindle fibers Which of the following could explain this 1 There could be a mutation that blocks the unattached kinetochore signal 2 There could be a mutation that prevents MAD from releasing CDC20 3 There could be too much CDC20 in the cell 4 There could be a mutation in Securin that prevents it from binding to Separase 5 There could be a mutation in CDC20 that causes it to attach Ubiquitin to Securin even when it is not bound to APC For each of the answers to the previous question are the mutations described gain of function or loss of function mutations A Gain of function B Loss of function 1 There could be a mutation that blocks the unattached kinetochore signal 2 There could be a mutation that prevents MAD from releasing CDC20 3 There could be too much CDC20 in the cell 4 There could be a mutation in Securin that prevents it from binding to Separase 5 There could be a mutation in CDC20 that causes it to attach Ubiquitin to Securin even when it is not bound to APC One idea for developing treatments for cancer is to identify drugs that block the metaphase to anaphase transition Which of the following could block the metaphase to anaphase transition 1 Drugs that block MAD from binding CDC20 2 Drugs that block APC from binding CDC20 3 Drugs that block the attachment of Ubiquitin to Securin 4 Drugs that block Separase from binding to Securin 5 Drugs that block MAD from releasing CDC20 Which of the following are true about mitosis chromosomes and cell division 1 Homologs are copies of chromosomes that come from di erent parents 2 Sister chromatids are copies of chromosomes made from DNA replication 3 Homologs are genetically identical but sister chromatids have some genetic di erences 4 Mitosis is the process that assures that cells formed from cell division are genetically identical 5 During anaphase homologs are separated and pulled to opposite poles by spindle bers 6 Each chromosome is a single long DNA molecule 7 Mis regulation of the metaphase to anaphase transition can lead to cells having the wrong number of chromosomes 8 When Cohesin is present cells must be in metaphase 9 Sister chromatids are made prior to mitosis 10 Cancer cells frequently have the wrong number of chromosomes Which of the following are true about the signaling pathway shown in the diagrams above 1 When the signal binds to the receptor it can never be released 2 Phosphates attached to the kinase proteins are held on by weak bonds and can be washed o 3 When the signal binds to the receptor it activates the receptor s kinase activity 4 The phosphates attached to the proteins come from ATP molecules and are not passed from one kinase to the next 5 When TFa is phosphorylated it moves from the cytoplasm into the nucleus Cancer patients on chemotherapy su er because chemotherapy drugs block DNA replication that must occur before mitosis can begin Which of the following would be true of the e ects of chemotherapy 1 Transit amplifying cells would be more severely a ected by chemotherapy than mature di erentiated cells 2 Cells of the digestive tract would be more severely a ected by chemotherapy than cells brain or heart 3 Chemotherapy patients would have sister chromatids in any of their cells that were dividing 4 Chemotherapy drugs would block kinases in the cell signaling pathway that causes stem cell self renewal divisions You analyze a cell with the signaling pathway shown above and nd the following TK1 is phosphorylated TFa is in the nucleus TK2 is NOT phosphorylated Which of the following could account for these observations 1 It could be that the signal never bound to the receptor 2 A loss of function mutation in TK1 could have blocked its kinase activity even when it is phosphorylated 3 A phosphatase could be present that targets TK2 4 A loss of function mutation in TK2 could block its kinase activity