This set of Cell Biology Multiple Choice Questions & Answers (MCQs) focuses on “Nucleic-acid Techniques”.
1. Which of the following is used to lyse the nucleus and release the DNA?
a) sodium dodecyl sulfate
b) ammonium sulfate
c) ferric phosphate
d) fluorine
View Answer
Explanation: Sodium dodecyl sulfate (SDS) is an anionic detergent used to lyse the nucleus and release their nuclear content. Release of DNA also increases the viscosity of the solution and SDS inhibits nuclease activity in the solution.
2. In purification steps of nucleic-acids, phenol is used for _______________________
a) deproteinization
b) denaturation
c) lowering pH
d) lowering viscosity
View Answer
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.
3. Which of the following is used to precipitate the nucleic acids?
a) glycerol
b) ethanol
c) methanol
d) ethylene
View Answer
Explanation: During the purification of nucleic acids after deproteinization of the sample, the nucleic acids are precipitated using cold ethanol. The RNA flocculates at the bottom whereas the DNA comes up at the interface between the saline and the ethanol interface.
4. Phenol is an active protein denaturant.
a) True
b) False
View Answer
Explanation: Phenol is an active protein denaturant that causes the proteins to lose their solubility and precipitate from the solution. It is used in the separation of nucleic proteins from a nucleic acid mixture.
5. Which type of gel is used for large nucleic acids?
a) acrylamide
b) cellulose
c) agarose
d) sephadex
View Answer
Explanation: Agarose gels are used for the separation of large nucleic acids using the technique of gel electrophoresis. Agarose gels have a greater porosity and make it easy for the larger proteins to migrate under the influence of an electric field.
6. Which technique is used to separate nucleic acids of size greater than 25 kb?
a) SDS-PAGE
b) Pulsed-field electrophoresis
c) 2D- gel electrophoresis
d) Isoelectric focusing
View Answer
Explanation: Native gel electrophoresis with agarose gels is used for the nucleic acids, while for larger nucleic acids with sizes greater than 25 kilobases, pulsed-field gel electrophoresis is usually used.
7. One Svedberg unit is equivalent to 10-13 ______________
a) hours
b) minutes
c) seconds
d) milli-seconds
View Answer
Explanation: One Svedberg unit is equivalent to a sedimentation coefficient of 10-13 seconds. Every particle moves with its specific sedimentation velocity in response to the centrifugal force.
8. In rate-zonal sedimentation, the nucleic acids are separated base on __________________
a) nucleotide length
b) relative charge
c) relative mass
d) mass-to-charge ratio
View Answer
Explanation: In rate-zonal sedimentation (also termed velocity-sedimentation), the nucleic acids (deoxyribonucleic acids and ribonucleic acids) are separated based on the lengths of their nucleotide sequence.
9. Equilibrium centrifugation is also known as ___________________ centrifugation.
a) isotonic
b) isopycnic
c) gradient
d) sucrose
View Answer
Explanation: Equilibrium centrifugation (also termed isopycnic centrifugation) separates the nucleic acid molecules based on their buoyant density. The gradient is established by using cesium chloride or cesium sulfate.
10. Which technique can be used to separate 15N and 14N?
a) Rate-zonal centrifugation
b) Isopycnic centrifugation
c) HPLC
d) Mass spectrometry
View Answer
Explanation: Isopycnic or equilibrium centrifugation can be used to separate nucleic acids having different base composition and even different isotopes of nitrogen such as 15N and 14N.
11. Nucleic acid hybridization is used to identify ________________________
a) RNAs
b) DNAs
c) Complementary base sequences
d) Proteins
View Answer
Explanation: Nucleic acid hybridization is the technique of identifying complementary base sequence of nucleic acids. Experiments involving nucleic acid hybridization require the incubation of two types of nucleic acid populations.
12. The procedure by which DNA gel is transferred to a membrane is termed as ___________________
a) blotting
b) centifugation
c) electrophoresis
d) paper chromatography
View Answer
Explanation: The procedure by which a DNA gel is transferred to a nitrocellulose membrane is termed as blotting. After fractionation of the nucleic acids by gel electrophoresis, the former are transferred to a nitrocellulose membrane.
13. In which of the following techniques, the DNA is labeled using complementary sequences and then analyzed using autoradiography?
a) Western blotting
b) Southern blotting
c) Isopycnic centrifugation
d) Spectrophotometry
View Answer
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.
14. Which of the following molecules can be analyzed using a northern blot?
a) RNA
b) Carbohydrates
c) Proteins
d) DNA
View Answer
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.
15. Which of the following is a commonly used label in blotting techniques?
a) vimentin
b) biotin
c) avidin
d) streptomycin
View Answer
Explanation: Biotin is a commonly used label in the blotting procedures. It is a small organic molecule that is covalently linked to the DNA backbone and can be identified by using the protein avidin (or streptavidin).
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