Podcast Beta
Questions and Answers
The Ames test is used to screen for carcinogenic compounds.
True
The conventional way to determine if a chemical is carcinogenic is to inject it into animals and look for tumor development.
True
The Ames test is used to measure the rate of forward mutations in strains of auxotrophic bacteria.
False
The Ames test is a cost-effective and efficient way to screen for carcinogenic compounds compared to animal testing.
Signup and view all the answers
All mutagenic agents are also carcinogenic.
Signup and view all the answers
The Ames test uses a strain of Salmonella typhimurium that is auxotrophic for histidine.
Signup and view all the answers
The first step in the procedure is to inoculate S. aureus from broth culture onto a nutrient agar plate.
Signup and view all the answers
The nutrient agar plate is incubated at 37°C for 48 hours.
Signup and view all the answers
A sterile colony carrier is used to transfer colonies from the initial S. aureus plate to new plates.
Signup and view all the answers
The replica plating technique allows detection of antibiotic-resistant organisms.
Signup and view all the answers
The streptomycin agar plate contains $100 \mu g$ of streptomycin per liter of medium.
Signup and view all the answers
After inoculating the plates, they are incubated at $37^\circ C$ for 2 to 4 weeks.
Signup and view all the answers
Ultraviolet radiation is part of the electromagnetic spectrum with longer, lower energy wavelengths than visible light.
Signup and view all the answers
When DNA absorbs UV radiation at 254 nm, the energy is used to form new covalent bonds between adjacent pyrimidines.
Signup and view all the answers
Thymine dimers are the most common type of pyrimidine dimers formed in DNA.
Signup and view all the answers
Escherichia coli uses light repair or photo-reactivation to reverse the formation of pyrimidine dimers in its DNA.
Signup and view all the answers
The presence of a few scattered revertants on the negative control plate is due to spontaneous back mutations, which never occur.
Signup and view all the answers
Examining the areas beyond the halo on the plate can help detect a faint lawn of bacterial growth.
Signup and view all the answers
The UV lamp should be turned off after 30 seconds for all plates.
Signup and view all the answers
Plates 6 and 7 should not be irradiated.
Signup and view all the answers
All plates should be incubated for 24 to 48 hours at room temperature.
Signup and view all the answers
Plate 4 should be irradiated for 3 minutes with the lid on and covered with the mask.
Signup and view all the answers
The growth patterns should be recorded on the Data Sheet after incubation.
Signup and view all the answers
The rate of reversion is determined by counting the number of colonies on histidine-deficient medium.
Signup and view all the answers
The top agar contains 0.6% agar, 0.5% NaCl, and histidine.
Signup and view all the answers
The histidine in the top agar allows the bacteria to undergo cell division for mutagenesis.
Signup and view all the answers
The top agar must be vortexed at high speed for even distribution.
Signup and view all the answers
The chemical agent can be applied directly to the center of the plate or using a filter paper disk.
Signup and view all the answers
If the agent is mutagenic, a halo of scattered colonies will be seen around the disk.
Signup and view all the answers
