This set of Vector Biology online test focuses on “Vectors and Cloning in Gram – Positive Bacteria – 6”.
1. A large number of antibiotics are made from the genus Streptomyces.
Explanation: Cloning in Streptomyces has attracted a lot of interest because of the large number of antibiotics that are made by the members of this genus.
2. Streptomyces coelicolor is _________ for genetic studies.
c) Not suitable
Explanation: Although Streptomyces coelicolor is the model species for genetic studies, many other species are the subject of intensive study.
3. Streptomycete DNA has a G+C content of _____ percent.
Explanation: Streptomycete DNA has a G+C content of 70-75% and this affects the frequency of restriction sites. AT-rich sites are rare.
4. AT-rich recognition sites are rare and this is useful if _______ fragments of DNA are desired.
Explanation: AT-rich recognition sites are rare and this can be useful if large-sized fragments of DNA are desired. Streptomycete DNA has a G+C content of 70-75%.
5. For the construction of gene libraries, which of the following sequence is not used?
Explanation: For the construction of gene libraries, the most commonly used enzymes are the ones with a high GC content in their recognition sequences.
6. Promoters in Streptomyces can be _______ during gene cloning.
Explanation: In Streptomyces, promoters may be several hundred base pairs upstream of the start of the gene and so can be lost during gene cloning.
7. Methotrexate is an analog of __________
c) Folic acid
Explanation: Methotrexate is a folic acid analog, which is a competitive inhibitor of the enzyme dihydrofolate reductase (DHFR).
8. Streptomyces genes are difficult to express in _________
Explanation: Streptomyces genes are difficult to express in E. coli because most promoters do not function and translation may be inefficient.
9. Transformation, transfection and conjugation are ways of introducing ________ into the cell.
Explanation: There are several ways in which DNA can be introduced into streptomycetes, including transformation, transfection and conjugation.
10. Which of the following helps in achieving higher plasmid DNA take up?
a) Polyethylene glycol
Explanation: Transformation is achieved by using protoplasts, rather than competent cells, and high frequencies of plasmid DNA uptake can be achieved in the presence of polyethylene glycol.
11. Expression of a heterologous gene in the T7 system is ____________
c) Not possible
Explanation: Expression of a heterologous gene in the T7 expression system can be made simpler by putting it directly under the control of the promoter.
12. Which of the following is the principal sigma factor?
a) Sigma A
b) Sigma B
c) Sigma C
d) Sigma D
Explanation: The number of sigma factors is different in each of the various genera but the principal sigma factor is sigma A. The composition of the core RNA polymerase is the same in most general.
13. Tandem sites are used for the recognition of _________
a) Alpha factors
b) Sigma factors
c) Beta factors
d) Gamma factors
Explanation: Many Streptomyces promoters are complex and may include tandem sites for recognition by different sigma factors. Streptomycetes are good at expressing genes.
14. With respect to mammalian cell cloning, salmon sperm DNA can serve as a source of ____________
a) Non-specific carrier
b) Specific carrier
c) Genomic DNA
d) Plasmid DNA
Explanation: Calcium phosphate transfection is mostly used and the specific donor DNA is often bulked with a non-specific carrier such as cleaved Salmon sperm.
15. What is the average size of single-stranded vector?
a) 6400 nucleotides
b) 1200 nucleotides
c) 2500 nucleotides
d) 5500 nucleotides
Explanation: The phage particles have dimensions 900*9 nm and contain a single-stranded circular DNA molecule, which is 6407 (M13) or 6408 (fD).
Sanfoundry Global Education & Learning Series – Vector Biology & Gene Manipulation.
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