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.
A. True
B. False
Answer: A
Clarification: 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.
A. Incapable
B. Model
A. Not suitable
D. New
Answer: B
Clarification: 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.
A. 10
B. 50
A. 70
D. 90
Answer: C
Clarification: 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.
A. Small
B. Mid-sized
A. Large-sized
D. Mixed
Answer: C
Clarification: 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?
A. BamHI
B. BglII
A. BelI
D. EcoR1
Answer: D
Clarification: 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.
A. Lost
B. Decreased
A. Increased
D. Inactivated
Answer: A
Clarification: 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 __________
A. Aminopterin
B. Kanamycin
A. Folic acid
D. Gentamycin
Answer: C
Clarification: 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 _________
A. Mammals
B. E.coli
A. Bacillus
D. Streptococcus
Answer: B
Clarification: 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.
A. DNA
B. Toxins
A. Enzymes
D. Host
Answer: A
Clarification: 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
B. Lactose
A. Sucrose
D. Galactose
Answer: A
Clarification: 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 ____________
A. Easy
B. Difficult
A. Not possible
D. Costly
Answer: A
Clarification: 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
A. Sigma C
D. Sigma D