Gene Manipulation Question Bank focuses on “Basic Laboratory Techniques – 6”.
1. In Western blotting, probe is mostly _______________
A. Toxic
B. Labeled
A. Unlabeled
D. Protein itself
Answer: C
Clarification: The probe is mostly unlabeled in the Western blotting technique, the detection or probing is hence usually done by a second molecule.
2. Protein A is obtained from _______________
A. Bacillus
B. Pseudomonas
A. Staphylococcus
D. E.coli
Answer: C
Clarification: The probe is often unlabeled and is itself detected in a sandwich reaction using a second molecule which is labeled, a species specific second antibody, for instance, protein A from Staphylococcus Aureus.
3. Protein A binds to __________________
A. IgG antibodies
B. Genes
A. Proteins
D. Membrane
Answer: A
Clarification: Protein A from Staphylococcus Aureus; which binds to certain subclasses of IgG antibodies. Protein A is actually a probe.
4. Dextran sulfate is a ____________
A. Antibody
B. Protein
A. Vector
D. Rate enhancer
Answer: D
Clarification: Dextran sulfate and other polymers act as volume excluders to increase both the rate and extent of hybridization.
5. Heparin is a _______________
A. Membrane
B. Rate enhancer
A. Antibody
D. Detergent
Answer: D
Clarification: Dried milk, heparin and SDS have been used to depress the non-specific binding of the probe to the membrane. Hence they are detergents as well as blocking agents.
6. The Denhardt’s solution does not use which of the following?
A. Ficoll
B. PVP
A. BSA
D. Heparin
Answer: D
Clarification: Denhardt’s solution, developed in 1966 consists of ficoll, polyvinylpyrrolidone and bovine serum albumin as detergents and blocking agents.
7. Denaturants are used for depressing _________________
A. Melting temperature
B. Freezing temperature
A. Boiling temperature
D. Denaturation
Answer: A
Clarification: Denaturants such as urea and formamide can be used to depress the melting temperature of the hybrid so that reduced temperature of hybridization can be used.
8. Formamide is used as a ___________ in Western blotting.
A. Rate enhancer
B. Denaturant
A. Antibody
D. Membrane
Answer: B
Clarification: Denaturants such as urea and formamide can be used to depress the melting temperature of the hybrid so that reduced temperature of hybridization can be used.
9. Heterologous DNA can increase non-specific binding.
A. True
B. False
Answer: B
Clarification: Heterologous DNA can reduce non-specific binding of probes to non-homologous DNA on the blot. This increases the overall efficiency.
10. Stringency can be regarded as a ________________
A. Toxic treatment
B. Specificity
A. Gel formation
D. Purification
Answer: B
Clarification: Stringency can be regarded as the specificity with which a particular target sequence is detected by hybridization to a probe.
11. Stringency is most commonly controlled by the temperature and ________________
A. Humidity
B. Salt concentration
A. Size of molecule
D. Antibodies
Answer: B
Clarification: Stringency is most commonly controlled by the temperature and salt concentration in post-hybridization washes.
12. The melting temperature TM is the temperature of ___________
A. Probe
B. Hybrid
A. Probe-hybrid
D. Antigens
Answer: C
Clarification: The melting temperature of a probe hybrid system can be calculated to provide a starting point for the determination of correct stringency.
13. What is the usual Tm (melting temperature) of long probes?
A. 30⁰
B. -25⁰
A. 25⁰
D. -30⁰
Answer: B
Clarification: With long probes, the hybridization is usually carried out at -25⁰C of melting temperature. When the probe is used to detect partially matched sequences, the hybridization temperature is reduced by 1⁰ for every 1% sequence divergence between probe and target.
14. A 1⁰ reduction is temperature is done for _____ percent divergence between probe and target.
A. 1
B. 5
A. 10
D. 100
Answer: B
Clarification: When the probe is used to detect partially matched sequences, the hybridization temperature is reduced by 1⁰ for every 1% sequence divergence between probe and target.
15. Which of the following can give a rapid hybridization rate?
A. Oligonucleotides
B. Nucleotides
A. Short probes
D. Long probes
Answer: A
Clarification: Oligonucleotides can give a more rapid hybridization rate than long probes as they can be used at a higher molarity.
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