Explore topic-wise InterviewSolutions in .

Correct OPTION is (b) gas and liquid

To explain: Critical drying point is the technique used to PREPARE samples for the scanning electron microscopy (SEM). At this point the DENSITY of the liquid and the gas is equal and hence there is no surface TENSION between the two.

Right choice is (b) Southern BLOTTING

Best explanation: Southern blotting is the technique where nucleic ACIDS are FIRST TRANSFERRED from gel to a nitrocellulose membrane. The membrane is then incubated in a solution of probes (complementary sequences) and then the bound sequences analyzed USING autoradiography.

The CORRECT OPTION is (b) X rays

The explanation is: Synchrotron is a HIGH energy cyclic-particle accelerator that PRODUCES X-rays as a by product. The highly focused X-ray beams generated are then used for creating diffraction patterns out of a protein crystal.

The correct answer is (d) trypsin

Easiest EXPLANATION: Trypsin is used in a mass spectrometric ANALYSIS to digest proteins. After protein digestion, there is a fractionation step USING the LIQUID chromatographic procedures. After that the samples are ionized and made gaseous.

The correct option is (b) diffuse through the column

For explanation I would SAY: The gel used for this technique used SMALL BEADS that are tightly packed in the column. This causes a small void to FORM between the beads. The proteins that are larger than the voids pass through or diffuse through the gel.

Right choice is (a) RNA

Easiest explanation: RNA molecules are analyzed using the northern blotting while DNA molecules can be analyzed using the SOUTHERN blotting. Western blotting is another TECHNIQUE in which ANTIBODIES are USED against proteins.

Right option is (a) True

Explanation: Every PROTEIN has a DIFFERENT solubility and it is a relative balance between the protein-solvent and protein-protein INTERACTIONS. The former causes the protein to REMAIN in solution, and the latter causes it to AGGREGATE.

Right choice is (c) calcium

The explanation: RECOMBINANT PLASMIDS are added to a BACTERIAL cell culture that is COMPETENT for taking up the plasmids from the medium. A culture can be made competent by treatment with calcium ions.

The correct option is (b) 1972

The best I can explain: The first RECOMBINANT DNA molecule was synthesized in the YEAR 1972 by Paul Berg, Herbert Boyer, Annie Chang, and Stanley Cohen of Stanford University and the University of CALIFORNIA, San Francisco.

Correct answer is (C) electric field

Explanation: Polyacrylamide gel ELECTROPHORESIS (PAGE) is a powerful technique that uses electric field to separate out PROTEINS in a matrix. SMALL organic MOLECULES of acrylamide are cross-linked to form a molecular sieve through which the proteins travel.

The correct answer is (a) protein-protein interactions

Easy explanation: The yeast two-hybrid SYSTEM is used for STUDYING protein-protein interactions. It was developed in 1989 by STANLEY Fields and Ok-kyu SONG at the State University of New York in Stony Brook.

The correct answer is (a) True

To ELABORATE: By disintegration of an atom, an alpha particle, beta particle or a gamma RADIATION may be EMITTED. Beta-particle is equivalent to an electron while the gamma radiation is the EMISSION of photons.

Correct CHOICE is (a) fluorochrome

Best explanation: Fluorochromes or fluorophores absorb the INVISIBLE, ultraviolet radiation and release a PORTION of the energy in long, visible wavelengths. RHODAMINE and fluorescein are examples of fluorochromes.

Correct CHOICE is (a) diffraction

To elaborate: The resolution attained by a MICROSCOPE is LIMITED by diffraction. DUE to diffraction, the light EMANATING from a sample can only be seen as a disk rather than a point of image.

Right option is (a) Yeast artificial chromosome

The explanation is: For cloning DNA SEQUENCES of a size LARGER than 20 to 25 KB, the conventional vectors such as plasmids and BACTERIOPHAGES can not be used. For the cloning of large DNA fragments, the yeast artificial chromosome (YAC) may be used.

The correct ANSWER is (b) non-soluble proteins

Explanation: Electron cryomicroscopy(also termed CryoTEM or cryo-EM). This technique is used mainly for non-soluble proteins and ORGANELLES such as RIBOSOMES. In this TECHNIQUES sample are studied at cryogenic temperatures.

Correct choice is (a) gaseous ions

For explanation I would say: For the mass spectrometric analysis of proteins, they are converted into positively-charged gaseous ions that are accelerated through a CURVED tube (under the INFLUENCE of a MAGNETIC FIELD) to a negatively-charged PLATE.

The correct option is (a) mobile, immobile

The explanation: In the liquid CHROMATOGRAPHY, there are two columns NAMELY the mobile PHASE and the immobile phase. The proteins bind to sites on the immobile (stationary phase) and pass through the COLUMN based on their affinity.

The correct answer is (c) specific activity

Easiest explanation: Purification of a PROTEIN can be MEASURED as an INCREASE in the specific activity of the protein. Specific activity is the RATIO of amount of that protein to the total amount of protein in that SAMPLE.

The CORRECT choice is (d) membrane RUPTURE

Explanation: Isotonic solutions have the same SOLUTE CONCENTRATION as inside the cell or ORGANELLE. This prevents the cell/organelle from osmotic pressure thus preventing lysis or rupture of membrane.

Right option is (c) tritium

To elaborate: Depending on the number of NEUTRONS PRESENT, the hydrogen has THREE ISOTOPES. Deuterium and tritium are its isotopes, out of which tritium contains two neutrons and is RADIOACTIVE.

Right choice is (a) True

The EXPLANATION: The isotopes have same number of protons but DIFFERENT number of neutrons in their NUCLEUS. HYDROGEN has three isotopes depending on the number of neutrons – 0, 1 or 2.

Right CHOICE is (a) reflect back

To ELABORATE: Unlike in transmission electron microscopy (TEM) in which image is formed when the ELECTRONS pass through the sample, in case of SCANNING electron microscope the electrons are reflected back and that leads to the FORMATION of an image.

The correct OPTION is (b) chromosomes

Explanation: The Feulgen stain was DISCOVERED by ROBERT Feulgen and is used to stain chromosomal material or DNA. For staining using the Feulgen stain, a prior HYDROLYSIS of the tissue in acid is required.

Correct answer is (a) tyrosine

Explanation: Spectrophotometry is a TECHNIQUE used to MEASURE the protein content of a sample. Out of the 20 AMINO acids that make a protein, two amino acids – tyrosine and PHENYLALANINE absorb light of 280 nm.

Correct OPTION is (b) False

Easy explanation: In polyacrylamide gel electrophoresis, a sieve of molecular MATRIX is formed through which the proteins migrate depending on their shape and size. The compact globular proteins move faster than the elongated FIBROUS proteins.

The correct answer is (a) True

The explanation: If a HOMOGENOUS CELL culture has the ability to GROW indefinitely in vitro, it is termed a cell line. Cell lines would NEVER undergo apoptosis and senescence. HeLa is a cancerous cell line derived from humans and was the first line to be MAINTAINED.

Correct option is (b) HEAVY metal

The best EXPLANATION: Osmium is a heavy metal that reacts with fatty acids leading to the preservation of membranes. Osmium tetroxide is used as a fixative in transmission ELECTRON MICROSCOPY.

Correct choice is (c) column

The best explanation: To prevent the premature scattering of ELECTRONS by collision with the GAS MOLECULES, a vacuum is generated through which the electrons travel, in the column PRIOR to operation.

Correct answer is (d) H. Gobind Khorana

Explanation: H. Gobind Khorana DEVELOPED synthetic techniques to SYNTHESIZE polynucleotides in the early 1960s as an attempt to DECIPHER the genetic code. COMPLETE bacterial tyrosine t-RNA was transcribed following the AFOREMENTIONED attempts.

Right ANSWER is (a) restriction endonuclease

To ELABORATE: The ENZYMES responsible for restricting the GROWTH of viruses in the bacterial cells. Restriction endonucleases were discovered in 1970s and have been an important tool in recombinant DNA technology EVER since.

Right option is (a) alpha

Easy explanation: Three different types of EMISSIONS are POSSIBLE for an ATOM that is disintegrating. ONE type of particles that may be released is the alpha particle that consists of two protons and two neutrons (EQUIVALENT to the nucleus of a helium atom).

The correct OPTION is (a) deproteinization

Easiest explanation: After the release of nuclear CONTENT of a cell, the next STEP is to free the nucleic acids from proteins and RNA. Phenol is used to deproteinize the SAMPLE; a mixture of phenol and chloroform may also be used.

The CORRECT option is (B) Nanosized tip

The EXPLANATION: The atomic force MICROSCOPE (AFM) uses a nanosized tip that PROBES the surface of materials. Atomic force microscopy is a technique of importance in molecular biology and nanotechnology.

Right choice is (b) phase-contrast MICROSCOPE

Best explanation: Living CELLS are small unstained samples that impose difficulty in visualization USING bright-field microscope. The HIGHLY transparent samples can be SEEN using the phase-contrast microscope.

The correct option is (a) True

To explain I would say: The image formed by the OBJECTIVE lens is used by the ocular lens as a SECOND lens system. The ocular lens FORMS an enlarged and virtual image. The third lens system located in the front part of the eyes uses this virtual image to FORM a real image on the retina.

Correct option is (b) transduction

To ELABORATE: Viral-mediated gene transfer is called transduction. In this PROCESS a non-replicating virus is allowed to infect a cell population which LEADS to the EXPRESSION of gene of INTEREST transiently.