In the case of monoclonal antibody production by hybridoma technology, myeloma cells used to lack the enzyme hypoxanthine-guanine phosphoribosyltransferase (HGPRT) such that fused can only survive when selected on hypoxanthine-aminopterin-thymidine (HAT). What is the role of aminopterin in this medium?

• To be used as cell cycle inhibitor of myeloma cells

• To block the pathway for nucleotide synthesis

• To facilitate fusion of myeloid B cells and antibody-producing B cells

• To facilitate production of antibody-producing B cells

In cells having G protein-coupled receptor inhibition of protein kinase A by siRNA technology ed to diminished transcription of androgen binding protein (ABP) and CREB protein. Addition of cAMP, which is a second messenger, will lead to

• increased transcription of ABP

• increased phosphorylation of CREB protein

• no change in transcription level

• increased GTPase activity of Gα subunit

53.

Binding of a ligand to a cell-surface receptor activates an intracellular signal transduction pathway through the sequential activation of four protein kinases. In the human cell line A, these kinases are held in a signaling complex by a scaffolding protein whereas, in another cell line B, these kinases are freely diffusible. Which one of the following possibilities do you think is NOT correct?

• The speed of signal transduction will be higher in cell A.

• The possibility of cross-linking with other signal transduction pathways will be lesser in cell A.

• Possibility of signal amplification will be higher in cell A.

• Potency of spreading signal through other signaling pathways will be higher in cell B.

Typical morphological defects are routinely used in genetic screens to identify novel genes in signal transduction pathways. Which one of the following morphology has been used to decipher the ethylene signaling pathways?

• Light grown morphology of seedling

• Tripple response morphology of seedling

• Dark grown morphology of seedling

• Morphology of true leaves

A set of neonatal mice are divided into four groups. Group 1 neonates were not primed with any antigen. Group 2 neonates were primed with KLH. Group 3 neonates were primed with KLH but thymectomized. Group 4 neonates were KLH-primed, thymectomized, but reconstituted with KLH-specific CD4⁺T cells. All these mice, when grown adult, were challenged with KLH and the anti-KLH IgG antibody was measured in sera. Which of the following is the correct order of magnitude of antibody response?

[> = greater than, ≥ = greater than or equal to]

• Group 1> Group 2 > group 3 > Group 4

• Group 2 > Group 1 > Group 3 ≥ Group 4

• Group 2 > Group 3 > Group 1 > Group 4

• Group 4 > Group 1 > Group 2 ≥ Group 3

An investigator discovers a new receptor for a known ligand and wanted to identify the binding partner of the receptor i.e. its co-receptor. The anti receptor antibody is not available but anti-GFP-antibody is available. Which one of the following strategies is most likely to identify the co-receptor?

• The GFP-receptor fusion protein is expressed in a cell line and analyzed by LC-MS/ MS.

• The GFP-receptor fusion protein is expressed in a cell line and the cells positive for GFP were sorted out, lysed and run on a polyacrylamide gel.

• The GFP-receptor fusion protein is coated on ELISA plate, followed by ELISA with an anti-GFP antibody.

• The receptor is cloned as a fucion protein of GFP and expressed in stimulated cells. The immuno-precipitated complex obtained by anti-GFP antibody was analyzed by LC-MS/ MS.

In the lysogenic state of λ phage

• both Cl and Cro are on

• both Cl and Cro are off

• Cl is on while Cro is off

• Cl is off while Cro is on

Which of the following phenomenon is observed in compatible plant-pathogen interactions?

• Virulence in pathogen

• Hypersenitive response in host

• Resistance in host

• Avirulence in pathogen

A tumour suppressor protein

• is one whose function brings about regression of a tumour

• is one where mutation are shown to cause or are associated with 

• is inactivated by oncogenes

• inhibits the progression of the cell cycle by phosphorylation cyclins

Immediate hypersensitivity reactions are associated with

• IgG

• IgE

• IgM

• IgA