This set of Gene Manipulation Multiple Choice Questions & Answers (MCQs) focuses on “Gene Sequencing”.
1. Chain-termination is a type of ______________
a) Sequencing
b) Vector generation
c) Antibiotic production
d) Gene manipulation
View Answer
Explanation: One of the commonest methods of sequencing is the Sanger sequencing which is also known as chain-termination.
2. The first significant DNA sequence to be obtained was that of ________
a) Lambda
b) Plasmid
c) Lactose
d) Mammals
View Answer
Explanation: The first significant DNA to be obtained was that of cohesive ends of lambda which were 12 bases long; in the year 1971.
3. Plus and minus sequencing is the other name for Sanger sequencing.
a) True
b) False
View Answer
Explanation: Plus and minus sequencing was used by Sanger in 1977 to sequence the 5386 base pairs long PhiX174 genome. This method was later superseded by Maxam Gilbert method.
4. Which type of DNA cleavage is done in the Maxam Gilbert method?
a) Edge
b) Interstitial
c) Base-specific
d) Gene-specific
View Answer
Explanation: The Maxam Gilbert method of sequencing was devised in 1977. It uses a variety of chemical reagents to bring about base-specific cleavage of DNA.
5. Sequence of which of the following cannot be determined using the Maxam Gilbert method?
a) Bacteria
b) Plants
c) Bacteriophage T7
d) Plasmid
View Answer
Explanation: Although Maxam Gilbert is a popular technique of gene sequencing and it superseded the Sanger sequencing method; it has not been used to sequence the genome of T7 phage.
6. What is the main enzyme component of Sanger sequencing?
a) Helicase
b) Polymerase
c) Nuclease
d) Gyrase
View Answer
Explanation: The chain-termination or dideoxy method of DNA sequencing capitalizes on two unique properties of DNA polymerase enzyme.
7. Which of the following is used by DNA polymerase as a substrate?
a) Sucrose
b) Lactose
c) Nucleotide
d) Nucleoside
View Answer
Explanation: The DNA polymerase enzymes used in the chain-termination method of sequencing can synthesize a complimentary copy of single-stranded DNA and can use nucleotides as substrates.
8. Which of the following act as chain terminator?
a) Exogenous
b) DNA
c) Deoxynucleotides
d) Dideoxynucleotides
View Answer
Explanation: A complementary strand is synthesized by the DNA polymerase and whenever an analog which is basically a dideoxynucleotide is incorporated in the growing chain, the chain is terminated.
9. The Klenow fragment is basically a _______________
a) DNA hybrid
b) DNA polymerase
c) RNA polymerase
d) Promoter
View Answer
Explanation: Klenow fragment is a DNA polymerase which is used in the Sanger sequencing method. It lacks the exonuclease activity, associated with intact enzyme.
10. ____________ is a chemically synthesized oligonucleotide.
a) Klenow fragment
b) DNA
c) Primer
d) RNA
View Answer
Explanation: Initiation of DNA synthesis requires a primer and usually this is a chemically synthesized oligonucleotide which is annealed close to the sequence being analyzed.
11. How many types of deoxynucleoside triphosphates are used in Sanger sequencing?
a) 1
b) 2
c) 3
d) 4
View Answer
Explanation: Four different types of deoxynucleoside triphosphates are used, one or more of which is labeled with phosphorus-32.
12. Prior to getting electrophoresed in the sequencing gel, DNA is ____________
a) Purified
b) Denatured
c) Synthesized
d) Fragmented
View Answer
Explanation: After a suitable incubation period for the DNA mix that contains deoxynucleoside triphosphates, dideoxynucleotides and sample DNA, the DNA is denatured before electrophoresis.
13. A sequencing gel is a ________________ gel.
a) Toxic
b) Highly-polymerized
c) High resolution
d) Low resolution
View Answer
Explanation: The sequencing gel is a high resolution gel designed to fractionate single-stranded DNA fragments on the basis of their size.
14. What is the molarity of urea used in sequencing gels?
a) 1 M
b) 3 M
c) 5 M
d) 7 M
View Answer
Explanation: The high-resolution sequencing gels can resolve fragments differing by just one base. These contain 6-20% acrylamide and 7 M urea.
15. The function of urea in the sequencing gels is to promote adherence.
a) True
b) False
View Answer
Explanation: The sequencing gels contain 6-20% acrylamide and 7 M urea. The function of urea is to minimize DNA secondary structure which affects electrophoretic mobility.
Sanfoundry Global Education & Learning Series – Vector Biology & Gene Manipulation.
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