This set of Molecular Biology Multiple Choice Questions & Answers (MCQs) focuses on “Plasmid DNA Replicates by Two Alternative Methods – 1”.
1. Transformation involves the uptake of _____________
a) Free DNA
b) Free RNA
c) Free tRNA
d) Free mRNA
Explanation: Transformation involves the uptake of the free DNA molecules. These DNA are released from one bacterium and taken up by the other to complete the process of transformation.
2. What is conjugation?
a) Transformation of DNA from a donor to recipient cell
b) Interchanging of two types of DNA
c) Transfer of DNA from recipient to donor
d) Uptake of DNA from hosts
Explanation: Conjugation occurs between two bacteria, one donor and one recipient cell. It involves the direct transfer of DNA from a donor cell to a recipient cell containing the F plasmid.
3. What is transduction?
a) Bacterial genes are transferred from donor to recipient cells
b) Bacterial genes are transferred from recipient to donor cells
c) Bacterial genes are carried from a donor cell to a recipient cell via bacteriophage
d) Uptake of naked DNA by hosts
Explanation: In transduction process bacteria is lysed. Thus the bacterial genes are carried from a donor cell to a recipient cell by a bacteriophage which undergoes a lytic lifecycle inside the host.
4. In which year Frederic Griffith discovered transformation?
Explanation: Frederick Griffith discovered transformation in Streptococcus pneumoniae in 1928. Pneumococci exhibited genetic variability in his experiments of causing pneumonia in rats.
5. During Frederick Griffith’s experiments what type of colonies were generated by the capsulated pneumococci?
a) Type R
b) Type L
c) Type S
d) Type B
Explanation: During the experiment, when grown in blood agar media in petridishes. Pneumococci with capsules form large, smooth colonies. These colonies are designated as type S colonies.
6. What is the function of the capsule of the bacterial cells?
d) Both A and B
Explanation: The polysaccharide capsule of the bacterial cell is required for virulence. It also provides protection to the bacterial cell from destruction by the host immune mechanism.
7. How many types of bacterial capsule are present for pneumococcus depending on the genotype of the cell?
Explanation: The polysaccharide capsule may be of several different antigenic types. This depends on the specific molecular composition of the polysaccharide and it also depends on the genotype of the cell.
8. The genetic information is stored in DNA rather than protein.
Explanation: The genetic information is stored in DNA. This was first discovered by Oswald Avery, Colin Macleod and Maclyn McCarty in 1944.
9. In the following which bacteria only take up their own DNA?
a) S. pneumoniae
b) B. subtilis
c) N. gonorrbacae
Explanation: S. pneumoniae and B. subtilis take up DNA from any source. Only H. influenzae and N. gonorrbacae takes up DNA from their own or closely related species.
10. How many copies of special short nucleotide pair sequences for identification are present in H. influenzae and N. gonorrbacae?
a) 100 copies
b) 600 copies
c) 500 copies
d) 1000 copies
Explanation: H. influenzae and N. gonorrbacae only takes up DNA from their own or closely related species. This is facilitated by the presence of a special short nucleotide pair sequences for identification which is present roughly about 600 copies in their respective genomes.
11. What do you mean by competent bacteria?
a) Able to take up genetic material from surrounding
b) Able to transfer genetic material to the surrounding
c) Takes up only its own genetic material
d) Can transfer genetic material from one bacterium to another
Explanation: There are some bacterial species that have the ability to take up DNA from their surroundings. These bacteria encode certain proteins that facilitate the process of this type of transformation. Such bacteria are known as competent bacteria.
12. Competence in a bacteria ___________
Explanation: The protein that mediates the transformation of the bacteria is known as competence and the bacteria are known as competent. This protein contains com segments.
Sanfoundry Global Education & Learning Series – Molecular Biology.
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