This set of Cytogenetics Question Bank focuses on “Cell Cycle Stages – 2”.
1. The Cln 3 receptors are located on ____________
a) DNA
b) Nuclear membrane
c) Cytosol
d) Nucleoplasm
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Explanation: A constant amount of Cln3 must be sensed for the cell to regulate its size. This is done via its receptors on DNA. As the amount of DNA is constant than when Cln3 exceeds a certain amount it will be free. Then it can trigger cell cycle.
2. Cell with DNA damage via a series of protein kinases __________
a) Activates CDC25
b) Inactivated CDC25
c) Activates WEE1
d) Inactivates WEE1
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Explanation: CDC25 is a phosphatase that removes the inhibitory phosphate on the S Cycin-CDk complex that leads to the activation. WEE1 kinase adds this phosphate leading to inactivation. DNA damage requires sop of cell cycle thus CDC2 which helps in progression is inactivated.
3. P53 binds to MAD2.
a) True
b) False
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Explanation: P53 binds to Mdm2 in normal cell which destroys the p53 leading to its reduction in concentration. On the other hand Mad2 bind to kinetochores that are not attached to microtubules.
4. Ataxia talengictesia is due to the defect in which of the following?
a) P53
b) Mdm2
c) Cdc25
d) Mad2
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Explanation: The defect in Mdm2 when it is unable to phosphorylate p53 in response to DNA damage causes ataxia talengictesia. It is a genetic disorder that often leads to cancer.
5. P53 activates transcription of _________
a) P5
b) p27
c) p21
d) p35
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Explanation: The increased amount of P53 as a result of DNA damage leads to increased transcription of WIP1/ Cip1p21 gene which leads to increase in p21 levels.
6. P21 is a CD1.
a) True
b) False
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Explanation: P21 is a CDI that binds to and inactivates the G1-S cyclin thus leading to the stop of cell cycle progression from G1 S phase.
7. The Spindle fibers in cell cycle are formed by ____________
a) Intermediate filaments
b) Microtubules
c) Actin
d) Myosin
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Explanation: The Microtubules are reassembled during cell division to form the spindle fibers. The spindle fibers bind to the chromosomes at the Kinetochores.
8. Which of the following gives a negative signal during anaphase?
a) Cdc25
b) Wee1
c) P53
d) Mad 2
View Answer
Explanation: Mad 2 bind to the kinetochores that are not bound to the spindle fibers. This is a negative signal. Removal of this negative feedback leads to anaphase.
Sanfoundry Global Education & Learning Series – Cytogenetics.
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