Find the missing number.

• 1

• 0

• 2

• 3

In solving a quadratic equation of the form x² + ax + b = 0, one student took the wrong value of a and got the roots as 6 and 2: while another student took the wrong value of b and got the roots as 6 and 1. What are the correct values of a and b, respectively?

• 7 and 12

• 3 and 4

• -7 and 12 

• 8 and 12

The distance between two oil rigs is 6 km. What will be the distance between these rigs in maps of 1:50000 and 1:5000 scales, respectively?

• 12cm and 1.2 cm

• 2 cm and 12 cm

• 120 cm and 12 cm

• 12 cm and 120 cm

Gram-negative bacteria, Klebsiella pneumoniae, upon infecting humans, results in severe septic shock after a few hours of infection. Which of the following is not true for this type of infection?

• Cell wall endotoxins cause overproduction of cytokines

• Septic shock can be treated by anti-TNFα antibodies.

• Recombinant bacterial proteins can be used for the treatment of septic shock.

• Recombinant TNFα receptor antagonists can be used for the treatment of septic shock.

Cells that grow and divide in a medium containing radioactive thymidine covalently incorporate the thymidine into their DNA during the S phase. Consider a simple experiment in which cells are labeled by a brief (30 minutes) exposure to radioactive thymidine. The medium is then replaced with one containing unlabeled thymidine, and the cells grow and divide for some additional time. At different time points after replacement of the medium, cells are examined under a microscope. Cells in mitosis are easy to recognize by their condensed chromosomes and the fraction of mitotic cells that have radioactive DNA can be estimated by autoradiography and plotted as a function of time after the thymidine labeling as in the figure below:

The rise and fall of the curve is because:

• The initial rise of the curve corresponds to cells that were just finishing DNA replication when radioactive thymidine was added (S phase).

• The peak of the curve corresponds to cells in M phase

• The rise in curve after 20 min corresponds to cells in the apoptotic phase.

• The fall in curve after 10 min indicates the cells exiting the M phase.

156.

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

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 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.

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

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.