This set of Molecular Biology Multiple Choice Questions & Answers (MCQs) focuses on “Many Plasmids Help their Host Cells”.
1. Where do the chimera molecules propagate?
a) Plasmid
b) Phagemid
c) Host
d) Carrier
View Answer
Explanation: Chimera or recombinant molecules needs a host for replication and propagation. Thus host selection is very essential for the propagation of a certain recombinant molecule.
2. Mutation sometimes assists the uptake of DNA material. It is a transformational regulator.
a) True
b) False
View Answer
Explanation: DeoR is a mutation that helps in the uptake of the DNA. This process is one of the transformational regulators and it also has a DNA binding activity.
3. What is the DNA sequence for cleavage by the endonuclease that is coded by hsdR?
a) AACGCNNTGC
b) AAGCCNNTGC
c) AGCCGNTTCC
d) ACGNNTGCTT
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Explanation: hsdR encodes for a type I restriction endonuclease. This endonuclease is known to identify the methylated sequence AACGCNNTGC.
4. In which of the following methylation dependent restriction system is necessary?
a) Type III
b) Type II
c) Type I
d) mcrA
View Answer
Explanation: Methylation dependent restriction enzymes are the products of mcrA, mcrB and mrr loci. It can degrade the sites that contain the methylated cytosine or adenine residue.
5. The DAM protein methylates which residue in the sequence GATC?
a) G
b) A
c) T
d) C
View Answer
Explanation: The DAM protein is responsible for the methylation of the newly formed DNA strands. It is known to methylate the adenine residue in the sequence GATC.
6. The quality and yield of plasmid DNA preparation both are enhanced by end A mutation.
a) True
b) False
View Answer
Explanation: The gene for DNA specific endonuclease is inactivated by the end A mutations. This mutation is sometimes induced in the host molecules which is seen to enhance both quality and yield of plasmid DNA.
7. What is the main characteristic that is present in a useful transformation method?
a) Property of plasmid
b) Ca2+ concentration
c) Efficiency of transformation
d) Availability of optimal physical conditions
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Explanation: All transformation methods cannot be used equivalently if the participants are not efficient. Thus efficiency of the vector and its complementary host is the most important factor in case of transformation which determines the range of transformants produced.
8. Plasmids contribute to the survivality of its host cells.
a) True
b) False
View Answer
Explanation: The genes contained in the plasmid are not of essential use for the bacterium for its day-to-day survival. Instead they help the bacterium to overcome stressed situations without which the bacterium may die.
9. Which of the following types of resistance is not provided by the plasmid for its host?
a) Antibiotic resistance
b) Heat resistance
c) Phage infection
d) Heavy metals
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Explanation: Resistance to phage infection requires the production of nucleases which is provided by the bacterial genome itself and not the plasmid. The resistances such as antibiotic, temperature, metal, toxic etc are provided by the plasmid DNA.
10. The drug, quinolone, resistance is observed in which of the following?
a) Klebsiella pneumoniae
b) Bacillus thuringiensis
c) Streptococcus pneumoniae
d) Staphylococcus lentus
View Answer
Explanation: Quinolone resistance gene is are frequently found on the plasmids that contain the ESBL genes. They provide resistance to substances such as aminoglycose, Qnr proteins etc. These resistances are provided in the plasmid containing bacterial family Enterobacteriaceae such as E. coli or Klebsiella pneumoniae.
11. Certain products produced by the plasmid genes can kill other microbes in its vicinity.
a) True
b) False
View Answer
Explanation: Some plasmids produce substances that kill other types of bacteria in its vicinity and improve its own multiplication. An example of this type of survivality is shown by the bacterium Agrobacterium tumifacience which produces a substance called opine which promotes the growth and multiplication of the same and decreases the growth of other bacteria.
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