Selectable Markers - Unsolved Practice Set
Chapter: Biotechnology Principles and Processes | Topic: Selectable Markers
SELECTABLE MARKERS - UNSOLVED PRACTICE SET
Topic: Selectable Markers
Multiple Choice Questions
Q1. A selectable marker in recombinant DNA technology is used primarily to:
- Cut DNA at specific sequences
- Identify and select only those host cells that have successfully taken up the vector (transformed cells)
- Replicate DNA molecules
- Translate mRNA into protein
Q2. A commonly used type of selectable marker gene confers resistance to a specific:
- Vitamin
- Antibiotic
- Vaccine
- Hormone
Q3. In the plasmid vector pBR322, genes conferring resistance to which two antibiotics are commonly used as selectable markers?
- Penicillin and streptomycin
- Ampicillin and tetracycline
- Only insulin-related genes
- Only growth hormone genes
Q4. Blue-white screening, a colour-based selection method, typically relies on the insertional inactivation of a gene coding for the enzyme:
- DNA polymerase
- Beta-galactosidase (lacZ gene)
- Restriction endonuclease
- RNA polymerase
Q5. In blue-white screening, bacterial colonies that appear white (rather than blue) on the selective medium typically indicate that the colony:
- Does not contain the plasmid at all
- Contains a plasmid with the foreign DNA successfully inserted into the marker gene, disrupting its normal function
- Contains only non-recombinant plasmids
- Has failed transformation completely
Short Answer Questions
Q6. What is a selectable marker, and why is it an essential feature of a cloning vector?
Q7. Give one example of an antibiotic resistance gene commonly used as a selectable marker in plasmid vectors like pBR322.
Q8. Briefly explain the principle behind blue-white screening as a selection method.
Q9. Why can't scientists simply assume that all host cells exposed to a vector during transformation have successfully taken it up?
Long Answer Questions
Q10. Explain the importance of selectable markers in recombinant DNA technology, describing how antibiotic resistance genes are used to identify transformed host cells.
Q11. Describe the process of blue-white screening in detail, explaining how insertional inactivation of the lacZ gene helps distinguish recombinant colonies from non-recombinant ones.
APPLICATION / ANALYSIS
Q12. A researcher transforms a batch of bacterial cells with a plasmid carrying an ampicillin resistance gene, then grows the bacteria on a nutrient medium containing ampicillin. Explain, using your understanding of selectable markers, why only the successfully transformed bacteria would be expected to survive and grow on this medium.
Q13. In a blue-white screening experiment, a researcher observes both blue and white bacterial colonies growing on the selective medium. Explain which colour of colony the researcher should select for further study if they are looking for bacteria that successfully incorporated the foreign gene of interest, and why.