The researchers grow and maintain the Ames test bacteria in liquid media containing histidine. They then prepare plates (semi-solid media) with media that lacks histidine. They also prepare tubes of media that is between the semi-solid and liquid media (soft agar) that contains trace amounts of histidine. They inoculate tubes of the soft agar with the mutant Ames test bacteria and add one of the following - 100 l of (1) chemical A in a solvent, (2) chemical B in a solvent, (3) sodium azide, a potent mutagen or (4) the solvent alone. They then pour the soft agar containing the bacteria and treatment onto a plate of media prepared without histidine. The bacteria quickly use up the histidine in the soft agar. The plates are kept in an incubator and colonies of bacteria are counted after a specified amount of time has elapsed. The experiment is repeated three times.
Which of the following groups is the experiment’s negative control? The group treated with…
A. Chemical A or chemical B in solvent
B. Sodium azide
C. Solvent alone
D. None of the above
Answer: Option C is correct.
Explanation:
A negative control ensures that none of the reaction conditions can
adversely affect the result.
In the given case, only solvent is used as a negative control to
ensure that the solvent as such has no effect on the reversal of
mutations.
Sodium azide is a known mutagen. It is used as a positive
control.
Chemical A and B are test samples.
The researchers grow and maintain the Ames test bacteria in liquid media containing histidine. They then...
LAB Genetic Engineering of Bacteria Problem Is it possible to transfer the allele for resistance to the antibiotic ampicillin into a bacterial cell? Objectives After completing this lab, the student will be able to: 1. Demonstrate micropipetting and sterile pipetting techniques for handling and transferring bacteria and plasmid DNA. 2. Maintain sterile conditions for culturing bacterial cells. 3. Inoculate bacteria into flasks, culture tubes, or agar plates. 4. Culture isolated individual colonies from an agar plate to form genetically identical...