471.

Given below are a few statements on Agrobacterium mediated transformation of plants. Which one of the following statements is CORRECT?

T-DNA transfer occurs from left border to right border
The gfp reporter gene can never be used for selection of transgenic plants
Transformation frequencies will decrease on overexpression of virulence genes.
Host plant genes play an important role in influencing transformation frequencies.

472.

Which one of the following assay systems can specifically detect apoptotic cells?

Tetrazolium dye (MTT) based colorimetric assay
FITC – annexin V based FACS analysis
51Cr release assay
Trypan blue exclusion assay

473.
From the various techniques listed below, which one CANNOT be used to precisely map the transcription start-site of a gene?

S1 Mapping

Sequencing the region downstream of promoter

5’ RACE

Primer Extension Method

B.

Sequencing the region downstream of promoter

S1 nuclease mapping is a nuclease protection assay using nuclease S1. This technique is used to quantify and map RNA transcripts. It is capable of identifying individual RNAs in a mixture of RNA sample of known sequence. It can particularly map introns and 5' and 3' ends of transcribed gene regions. Primer extension is a method typically used to map the 5' end(s) of an RNA, thus defining the transcription start site and providing initial evidence for where the promoter is located within a cloned gene. RACE results in the production of a cDNA copy of the RNA sequence of interest, produced through reverse transcription, followed by PCR amplification of the cDNA copies (RT-PCR). The amplified cDNA copies are then sequenced and, if long enough, should map to a unique genomic region. RACE with high-throughput sequencing was first introduced in 2009 as Deep-RACE to perform mapping of Transcription start sites (TSS) of 17 genes in a single cell-line. However, sequencing the region downstream of promoter cannot be used to map transcription start site.

474.

A group of scientists performed an experiment where they artificially fused mouse cells with monkey cells. The resulting fused cells were labelled with fluorescently tagged antibodies against mouse and monkey surface receptor proteins, X and Y respectively. At the time 0 minute just after fusion events, two receptors were confined to their own half in the heterokaryon. However, such surface receptors (X and Y) intermixed on the cell surface after 60 minutes. Which one of the given statements correctly reflects the outcome of the experiment?

The ptoteins in cytoplasm are in a dynamic state.
The proteins on the membrane surface are in a dynamic state.
Surface membrane proteins exchange with the cytosolic proteins.
Membrane surface proteins are in a static phase.

475.

In order to detect minor variations in antigen concentration, the following procedures were suggested. Which one will likely be the best option?

Antigen coated microtitre well → add antibody → add enzyme conjugated secondary antibody → add substrate and measure colour.
Antibody coated microtitre well → add antigen →add enzyme conjugated secondary antibody → add substrate and measure colour.
Preincubate antigen with fixed amount of antibody → add to antigen coated well → add enzyme conjugated secondary antibody → add substrate and measure colour.
Preincubate antigen with fixed amount of antibody → add to antibody coated well →add enzyme conjugated secondary antibody → add substrate and measure colour.

476.

Three students (P, Q, R) in a research lab were trying to identify proteins that interact with a transcription factor X. P performed gel filtration experiments and identified that X was found along with proteins A, B, C and D. Q performed coimmunoprecipitation experiments using antibodies to X and identified A, B and C. R did a yeast-2-hybrid screen and identified only B.

The following are likely conclusions that may explain all the results:

(i) A, B, C and D are in a complex with X.

(ii) X directly interacts with B.

(iii) Only A, B and C are in complex with X.

(iv) D is probably weakly associated with X. Which of the above conclusions best explains all the results?

(i), (ii) and (iii)
(i), (ii) and (iv)
(i), (iii) and (iv)
(ii), (iii) and (iv)

477.

Sub-cellular fractionation-based assays have been used to identify various organelles in the mammalian cells. In order to characterize such organelles in a living mammalian cell, which of the following microscopy-based method would be the most accurate?

use of fluorescent probes specific for organelles.
use of organelle specific fluorescent probes followed by microinjection of fluorescent antibodies against organelle specific protein.
use of fluorescent probes in permeabilized cells.
use of organelle specific fluorescent probes followed by cryoelectron microscopy

478.

From the following statements,

(a) Surface plasmon resonance can be used to determine binding constants only in the range of 10² – 10³ M.

(b) de novo sequencing is not possible by mass spectral methods.

(c) The position of hydrogen atoms in proteins is not directly determined by X-ray, diffraction.

(d) Circular dichroism and nuclear magnetic resonance spectroscopy do not give the same information on protein structure.

Choose the option with all correct statements.

(a), (b), (c)
(a), (c), (d)
(b), (d)
(c), (d)

479.

In order to visualize the intracellular organization of a cell, one can utilize various microscopy-based techniques. These include:

(a) Differential interference contrast (DIC) microscopy

(b) Phase contrast microscopy

(c) Dark field microscopy

(d) Epifluorescence microscopy

(e) Scanning electron microscopy

(f) Transmission electron microscopy

(g) Confocal microscopy

Which of the above mentioned microscopes can be used to study the intracellular dynamics using live cell imaging?

(a), (b), (e), (f), (g)
(a), (b), (c), (d), (g)
(a), (d), (e), (f), (g)
(c), (d), (e), (f), (g)

480.

Which one of the following set of essential components are required for Sanger method of DNA sequencing in a required buffer containing MgCl₂ and Tris-HCl?

DNA template, a primer, 4 deoxyribonucleotides, 4 labelled dideoxyribonucleotides, DNA polymerase
DNA template, a primer, 4 labelled dideoxyribonucleotides, DNA polymerase, DNA ligase
DNA template, 4 deoxyribonucleotides, 4 labelled dideoxyribonucleotides, DNA polymerase, DNA ligase.
DNA template, a primer, 4 labelled dideoxyribonucleotides, DNA polymerase, telomerase.