This set of Microbiology Multiple Choice Questions & Answers (MCQs) focuses on “Bacterial Transformation”.
1. What are the characteristics of rough pneumococci strain?
a) noncapsulated and pathogenic
b) noncapsulated and nonpathogenic
c) capsulated and pathogenic
d) capsulated and nonpathogenic
Explanation: Griffith injected mice with a few rough (noncapsulated and nonpathogenic) pneumococci and a large number of heat-killed smooth cells.
2. In Griffith’s experiment which of the following strains of pneumococci was isolated from dead mice?
a) live rough cells
b) dead rough cells
c) live smooth cells
d) dead smooth cells
Explanation: When Griffith injected mice with a mixture of a few rough and a large number of heat-killed smooth cells of pneumococci, then the mice subsequently died of pneumonia, and live smooth cells were isolated from their blood.
3. Which of the following things was identified as the transforming principle?
Explanation: Griffith showed in his experiment that DNA was the transforming principle that transformed the living rough bacteria into pathogenic smooth ones.
4. We require cell-free DNA for transformation to take place.
Explanation: Transformation is the process whereby cell-free or naked DNA containing a limited amount of genetic information is transferred from one bacterial cell to another.
5. What should be the minimum weight of DNA that is required for a successful transformation?
a) 1000 daltons
b) 100,000 daltons
c) 300,000 daltons
d) 8 million daltons
Explanation: Molecular weights of DNA in the range of 300,000 to 8 million daltons have been shown to result in successful transformation.
6. How many DNA molecules are transferred after each transformation?
Explanation: Each transformation results from the transfer of a single DNA molecule of double-stranded DNA.
7. Which of the following enzymes acts on the DNA after its entry into the cell?
Explanation: After DNA entry into a cell, one strand is immediately degraded by deoxyribonucleases, while the other strand undergoes base pairing with a homologous portion of the recipient cell chromosome.
8. Which among the following species have not been transformed?
Explanation: Bacterial species that have been transformed include, besides Streptococcus pneumonia, those in the genera Bacillus, Haemophilus, Neisseria, and Rhizobium.
9. In which phase of growth does the recipient cell take up the donor DNA?
a) lag phase
b) early logarithmic phage
c) late logarithmic phage
d) stationary phage
Explanation: Conditions suitable for uptake of donor DNA into recipient cells occur only during the late logarithmic phase of growth.
10. The DNA uptake process does not require any energy.
Explanation: The uptake process has been found to be an energy-requiring mechanism because it can be inhibited by agents that interfere with energy metabolism.
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