This set of Cytogenetics Questions and Answers for Entrance exams focuses on “Apoptosis and Cancer – 2”.
1. Which of the following is not a part of DISC complex?
a) Fas Ligand
b) Fas receptor
d) Procaspase 8
Explanation: The DISC complex (death-inducing signalling complex ) consists of the fas ligand and receptor that forms the Death domain. This in turn aggregates and activates procaspase 8 to caspase 8. Cytochrome is not directly a part of DISC complex.
2. h of the Bcl-2 family protein can caspase 8 act on?
Explanation: Bid, when acted upon by caspase 8 will give the truncated version of Bid- tBid. tBId can move to the mitochondria and release cytochrome which will turn on the intrinsic pathway of apoptosis.
3. P53 has a high turnover number.
Explanation: In the normal cell p53 can interact with Mdm2 which acts as specific E3 ubiquitin ligase for p53 and ubiquitination leads to destruction of p53. It thus has a high turnover number and doesn’t accumulate in healthy cells.
4. Epstein Barr virus can cause cancer by________________
a) Producing p53 binding protein
b) Inducing cytochrome release from mitochondria
c) Producing anti-apoptotic protein
d) Producing adaptor protein in excess
Explanation: EBV produces a protein similar to Bcl-2, i.e. an anti apoptotic protein. It also increases the production of Bcl-2 protein itself. Thus,, b disrupting the pro-apoptotic / anti-apoptotic balance apoptosis is induced.
5. An E6 factor which binds to p53 and thus causes cancer is seem in case of _____________
a) Epstein Barr Virus
b) Human Papilloma Virus
Explanation: HPV or Human Papilloma cells produce the E6 factor which binds p53. This in turn prevents the activation of apoptotic pathway triggered by DNA damage and leads to cell proliferation and cancer.
6. Which caspase is activated in the ER pathway of apoptosis?
a) Caspase 3
b) Caspase 7
c) Caspase 8
d) Caspase 12
Explanation: In extreme hypoxic conditions, the TRAF2 in the ER releases the associated procaspase 12; activated caspase 12 and leads to apoptosis.
7. Downregulation of caspase 9 is seen in ________________
b) Breast cancer
c) Colorectal cancer
d) Lung cancer
Explanation: Reduced functioning of caspases may prevent apoptosis thus leading to cancer. Down regulation of caspase 12 is seen mostly in case of colorectal cancers.
8. Which of the following is true for cells with DNA damage?
a) P53 binds to Mdm 2
b) Mdm2 is prosphorylated
c) p53 acts as transcription factor for Bad
d) p53 is ubiquinylated
Explanation: In cells with DNA damage chk1 and chk2 kineses phosphorylated Mdm2. Phosphorylated Mdm2 can no longer bind p53 whose level now rises.
9. Downregulation of caspase 3 can lead to ovarian cancer.
Explanation: It has been reported that caspase-3 mRNA levels are appreciably downregulated in breast, ovarian, and cervical tumours. Low levels of caspases or impairment in caspase function may lead to decreased apoptosis.
10. P53 accumilation activates which polymerase to repair DNA damage?
a) Pol alpha
b) Pol Beta
c) Pol kappa
d) Pol eta
Explanation: On sensing the DNA damage p53 level rises which stimulate GADD45 and pol k which tries to repair the DNA damage. Only when the damage is too much to repair apoptosis is triggered.
11. Decoy molecules which binds to Fas L are seen in _______________
a) Lung cancer
c) Breast cancer
d) Ovarian cancer
Explanation: In lung cancer and in colon cancer we see ‘decoy’ molecule that binds to the Fas ligand. Thus, the ligand can no longer induce apoptosis by interacting with the Fas receptor.
12. The target for Obimerson sodium is _________
Explanation: Obimerson sodium when given with normal chemotherapeutic drugs is a Bcl-2 antisense oblimer. It prevents the expression of Bcl2 anti-apoptotic proteins in proliferative cells leading to apoptosis.
13. Tenovins are__________________________
a) Bcl2 sequestering
b) Cytochrome releasing
c) Mutant p53 repairing
d) p53 activating
Explanation: When tenovin is administered, this small molecule activates p53 which in turn leads to apoptosis. This is used as a drug to treat cancer.
14. Pikan083 can act on p53 mutants and induce cancer.
Explanation: Mutant p53 doesn’t bind to the promoter and hence can’t induce apoptosis by transcribing. Pikan083 can bind to and activate mutant p53 in proliferative cells leading to their apoptosis.
Sanfoundry Global Education & Learning Series – Cytogenetics.
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