These are questions from cell molecular biology , and it requires some extensive
ID: 69665 • Letter: T
Question
These are questions from cell molecular biology, and it requires some extensive knowledge. I have tried finding the answers myself online and in my book, so this is the last thing I know to do. I need detailed explanations PLEASE!!!!! Someone please help!!!! Thank You!!!!
Microtubules are stabilized by which nucleoside
ADP
ATP
CTP
GTP
UTP
The protein that normally inhibits the protease activity required for separation of sister chromatids is
a. APC
b. cohesin
c. M-cyclin
d. securin
e. separase
P53 can inhibit uncontrolled growth due to DNA damage by all of the following except
a. activate immune system
b. inhibit cell division
c. prompt apoptosis
d. trigger DNA repair
e. all of the above
Explanation / Answer
The basic unit of microtubule is tubulin heterodimer. The tubulin binds to GTP but does not hydrolyze it. The tubulin subunit hydrolyzes the bound GTP to GDP and Pi to provide necessary energy. Like tubulin the actin monomers bind to ATP and hydrolyze ATP to ADP and Pi. The resultant ADP stabilizes the microtubules. Hence, option 1 is correct.
In Sacharomyces cerevisiae, the cohesion of sister chromatids is regulated by a protein called Pds1p or securin. The Pds 1p or securin binds to a protease Esp 1p and inhibits it. The Esp 1p is known as separin or separase. When anaphase begins the anaphase protein complex degrades the securin protein. Hence, Option e is correct.
P53 is tumor suppressor protein that protects DNA from damage by initiating repairing mechanism inhibits cell division by arresting CDK2 at G1/S cell cycle check point and prevents DNA damage and regulates cell division. Under irreparable condition of DNA damage it initiates the cells to undergo apoptosis but it is not involved activation of immune system. Hence, option (a) is correct.
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