You are working with an in vitro eukaryotic transcription system, which produced both capped and uncapped mRNAs. You incubated these mRNAs with mammalian cell nuclear extract and then quantified the different products as shown below. Which of the following graphs correctly represents the expected result?

A rapidly growing bacterial species such as E.coli exhibits a typical phase of the growth cycle in liquid nutrient broth (lag phase → log phase → stationary phase → death phase). If a bacterial culture has a starting density of 10³ cells/ ml has a lag time of 10 minutes and a generation time of 10 minutes, what will be the cell density be at (cells/ml) 30 minutes?

• 6.0 × 10³

• 2.0 × 10³

• 3.0 × 10³

• 4.0 × 10³

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.

In order to study the role of telomers in DNA replication, genetically engineered mice were prepared, where the gene for telomerase RNA was knocked out. When cells from these knock out mice were taken and cultured in , they proliferated even after 100 cell divisions which is quite unlikely in the case of human cells.

Which of the following is the correct reason?

• Humans and mice are fundamentally different with respect to their requirements for telomerase in the context of DNA replication.

• In vitro, mice DNA becomes circular due to end to end chromosomes fusion and does not require telomerase for DNA end replication.

• Mice have very long stretch of telomere DNA sequence compared to that of humans.

• In vitro, mice DNA replication does not require the removal of RNA primers

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

During the elongation step of protein synthesis, translocation moves the mRNA and the peptidyl t-RNA by one codon through the ribosome. Translocation in E.coli involves GTP and EF-G. However, in vitro translocation can take place independent of GTP and EF-G. Based on these observations, the following hypotheses can be made:

(A) The molecular mechanism of translocation in vitro is completely different from that in vivo.

(B) Translocation activity is independent of GTP hydrolysis.

(C) Translocation activity is completely dependent on GTP and EF-G.

(D) Translocation activity is inherent in ribosomes, however, the rate of translocation in vivo is enhanced significantly in the presence of GTP and EF-G.

Which one of the following combinations is correct?

• only (D)

• (A) and (C)

• (A) and (B)

• (C) and (D)

Cells undergo apoptosis by two distinct and inter-connected pathways: extrinsic and intrinsic. The extrinsic pathway is activated by extracellular ligand binding to cell surface death receptors. Whenever an apoptotic stimulus activates intrinsic pathway, the pro-apoptotic Bax and Bak proteins become activated and induce the release of cytochrome C from mitochondria leading to caspase cascade activation resulting in apoptosis. In cell A, cytochrome C is introduced by microinjection whereas in cell B, cytochrome C is introduced by microinjection but Bax and Bak are inactivated. What will be the most appropriate apoptotic response type in both cells?

DNA methylation plays an important role in transcription regulation in vertebrates. There is an inverse correlation between the level of DNA methylation in the vicinity of a gene and its transcription rate, whereas there is a direct correlation between histone acetylation and increased transcription. β-thalassemia is a common genetic impairment of hemoglobin β-chain synthesis in humans. If these patients can synthesize hemoglobin-F instead of hemoglobin β-chain in its place, the would-be notably benefited. Administration of 5-azacytidine to β-thalassemia patients increases hemoglobin-F level in erythrocytes and thus benefit the patients.

Which one of the following statements about 5-azacytidine is NOT correct?

• Cells exposed to 5-azacytidine incorporate it into DNA in place of cytidine.

• 5-azacytidine decreases DNA methylation.

• 5-azacytidine promotes histone acetylation.

• 5-azacytidine does not promote gene expression

A non-enzymatic viral protein X was found to be inducing a cellular gene promoter activity. Although no in vitro DNA binding activity could be identified with X protein, it was found to be co-recruited on the cellular promoter along with a cellular transcription factor in vivo.

Which one of the following statements seems to be best interpretation of the above findings?

• X is a DNA-binding protein

• X physically interacts with the transcription factor.

• X modifies the chromatin for transcription activation.

• X is a chaperone.

Mouse erythroleukemia (MEL) cells are used as an in vitro cell culture model for understanding erythropoietin. These cells are arrested at the stage of pro-erythroblast due to transformation. These cells could be induced by heme to differentiate further so as to synthesize hemoglobin. the most probable molecular mechanism for this could be that heme may suppress and/ or downregulate an endogenous heme-regulated inhibitor (HRI) kinase, an inhibitor of globin synthesis. This downregulation in turn promotes differentiation.

To validate this hypothesis which of the following approaches is NOT appropriate?

• Transfect MEL cells with HR1 kinase gene.

• Knock down HR1 kinase gene in MEL cells.

• Determine the rate of protein synthesis in situ as a function of differentiation.

• Measure HR1 kinase activity as a function of differentiation.