Cellular level of tumour suppressor protein p53 is maintained by the ubiquitin ligase protein, Mdm2. Over expression of Mdm2 was found to convert a normal cell into cancer cells by destabilizing p53. Another protein 19^ARF inhibits the activity of Mdm2 thus stabilizing p53. Loss of p19^ARF function also converts normal cells into cancer cells. Based on the above information, which one of the following statements is correct?

• Both MDM2 and 19^ARF are oncogenes.

• Both MDM2 and 19^ARF are tumour suppressor genes.

• MDM2 is an oncogene but 19^ARF is a tumour suppressor gene.

• 19^ARF is an oncogene but MDM2 is a tumor suppressor gene.

G-protein coupled receptors (GPCR) consist of three protein subunits α, β, and γ. In unstimulated state, α subunit is GDP bound and GPCR is inactive. When GPCR gets activated, it like guanine nucleotide exchange (GEF) factor and induces α-subunit to release its bound GDP allowing GTP to bind in its place. In order to regulate G-protein activity by regulating GDP/ GTP concentration, α subunit acts as

• GTPase

• GDP kinase

• cGMP-specific phosphodiesterase

• cAMP-specific phosphodiesterase

Which one of the following statements about the nuclear receptor superfamily is NOT true?

• The receptors are always cytosolic, where they remain associated with heat-shock proteins and have variable ligand-binding domains in the N-terminal region.

• The receptors have characteristic repeat of the C₄ zinc-finger motif.

• The receptors are either homodimeric or heterodimeric, and in the absence of their hormone ligand, the heterodimeric receptors repress transcription, when bound to their response elements.

• The receptors have a unique N-terminal region of variable length and may contain a nuclear localization signal between the DNA- and ligand0binding domains.

Which of the following is NOT a second messenger?

• Cyclin GMP

• Diacylglycerol

• Inositol triphosphate

• Phosphatidylinositol

Which of the following is NOT a cell adhesion protein?

• Cadherin

• Selectin

• Immunoglobulin (Ig) superfamily

• Laminin

The mutation in an oncogene falls under which of the following classes?

• Loss of function mutation

• Frame shift mutation

• Gain of function mutation

• Dominant negative mutation

Cytotoxic T cells express

• CD8 marker and are class II MHC restricted

• CD4 marker and are class I MHC restricted

• CD4 marker and are class II MHC restricted

• CD8 marker and are class I MHC restricted

108.

A diabetic patient has a blood glucose level due to reduced entry of glucose into various peripheral tissues in addition to other causes. There is no problem of glucose absorption, however, in the small intestine of these patients. The following statements are put forward to explain this observation:

A. Glucose is transported into the cells of muscles by glucose transporters (GLUTs) which are influenced by insulin receptor activation.

B. Glucose transport into the enterocytes is mediated by sodium-dependent glucose transporters (SGLTs) which are not dependent on insulin.

C. Glucose molecules are transported in the small intestine by facilitated diffusion.

D. The secondary active transport of glucose in muscles.

Which one of the above statement(s) is INCORRECT?

• Only A

• A and B

• Only C

• C and D

Following are certain statements that describe plant-pathogen interactions:

A. Hemibiotrophic pathogens are characterized by initially keeping host cells alive followed by extensive tissue damage during the later part of the infection.

B. Effectors are molecules present in host plant that act against the pathogen attack.

C. Plants possess pattern recognition receptors (PRRs) that perceive microbe-associated molecular patterns (MAMPs) present in specific class of microorganisms but are absent in the hosts.

D. Phytoalexin production is a common mechanism of resistance to pathogenic microbes in a wide range of plants.

Which one of the following combinations is correct?

• A, B, and C

• A, C, and D

• B, C, and D

• A, B, and D

Cancer is often believed to arise from stem cells rather than fully differentiated cells. The following are certain views related to the above statement. Which one of the following is NOT correct?

• Stem cells do not divide and therefore require fewer changes to become a cancer cell.

• Cancer stem cells can self-renew as well as generate the non-stem cell populations of the tumor.

• Teratocarcinomas prove tumors arise from stem cells without further mutation.

• Stemness genes can often function as oncogenes.