Cell biology 1. A bacterial artificial accepts DNA insert up to A) 10,000 kb B)
ID: 146628 • Letter: C
Question
Cell biology 1. A bacterial artificial accepts DNA insert up to A) 10,000 kb B) 5,000 kb C) 1,000 kb D) 500 kb E) 10 kb 2. What type of fluorescence microscopy utilizes high-resolution imaging? A) Light microscopy B) Phase-contrast microscopy C) Electron microscopy D) Laser scanning confocal microscopy E) STORM 3. If the microscope has an objective lens with a magnification of 50X and an ocular lens with a magnification of 4X, what is the total magnification of the image? A) 8X B) 50X C) 58x D) 200X E) 400X 4. Which of the following technique(s) allow one to study protein-protein interactions? A) Light microscopy D) Gel electrophoresis E) 2D gel electrophoresis 5. If you wanted to do a two-step protein purification (sequentially using two columns) based first on charge followed by- and then on size, you would do A) Gel filtration chromatography, ion exchange chromatography B) Gel filtration chromatography; affinity chromatography C) lon exchange chromatography, affinity D) lon exchange chromatography: gel filtration chromatography E) Affinity chromatography: gel filtration chromatography 6. Fractionation of nucleic acids by ultracentrifugation can be accomplished by A) Gel electrophoresis B) Velocity sedimentation D) A and B E) B and C 7. What type of cell culture system best recapitulates the in vivo environment from which cells originally were isolated? A) Primary culture B) Secondary culture C) 2D culture D) 3D culture E) None of the above Page IExplanation / Answer
1. BAC can accept inserts upto 300kb. They contain origin of replication from F plasmid.
2.laser scanning confocal microscopy. Laser light is focussed on a particular plane (focal plane) by objective lens and final image is obtained by collecting light from this point. A pin hole aperture placed before the detector filters out of focus light coming from above and below the focal plane. This produces high resolution images as out of focus light is eliminated and light from a single plane is used to create the image. In normal microscopes light from all planes throughout the thickness of the specimen contribute to image formation.
3. Total magnification of a compound microscope = magnification of objective lens x magnification of ocular lens
= 50x X 4x
= 200x
4. Co-precipitation allows the study of protein-protein interactions. In this method an antibody specific for a particular protein (A) is immobilized on a support to precipitate A. If protein A interacts with another protein B then precipitation of protein A with anitbody will co-precipitate B. Then the coprecipitated complex can be separate by SDS-PAGE to be observe two different bands by protein A and B.
5. Ion exchange and then gel filtration chromatography. Ion exchange is used to separate proteins with different surface charge. Ion exchange colums are of two types : cation exchange and anion exchange . Cation exchanger is negatively charged and binds to positively charged cationic proteins and repels negatively charged protein. Anion exchanger is positively charged and binds to negatively charged anionic proteins and repels positively charged proteins. In this way its helps in separation of proteins on basis of charge.
Gel filtration chromatography separates protein molecules on the basis of size. It contains column packed with porous beads and proteins will small size enter the small pores of the beads. Large proteins are unable to enter the pores. Small proteins have a longer transit time in the column and larger proteins unable to enter pores have shorter transit time in the column. Therefore large proteins elute first and small elute later.
6. B and C, Nucleic acid can be fractionated by ultracentrifugation by both velocity and equilibrium sedimentation. Both are types of density gradient centrifugation. In velocity sedimentation a preformed gradient is used to separate particles on the basis of their mass or size. In equilibrium sedimentation particles are separated according to their buoyant density and not their size. This helps in separation of two similiar sized particles with different buoyant density.
7. Primary culture. A primary culture involves in vitro cultivation of cells directly isolated from tissue/organ/organism. Therefore they more closely mimic the in vivo physiology of cells.
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