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24 Cards in this Set
- Front
- Back
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Mutagen |
Chemical substance or physical Agent capable of altering the nucleotide sequence of DNA , |
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Carcinogens |
Mutagen that cause mutations in genes that are capable of producing cancerous cells |
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Back mutation |
Second mutations that restores the bacteria to normal wild-type |
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His- |
Pre-muted bacteria that cannot make the amino acid Histidine |
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His+ |
Bacteria is able to produce the amino acid Histidine |
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Ames test |
Test that uses bacteria to show whether or not a certain chemical substance is a mutagen |
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A small percentage of mutations that occur due to errors in DNA replication is called? |
spontaneous mutations |
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Increased amount of mutations above spontaneous mutations due to mutagens increasing the rate of DNA errors are called? |
induced mutations |
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What bacteria is used in the Ames test? |
Salmonella typhimurium his- |
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What makes the bacteria selective? |
Strains of mutation prevents bacteria from making the amino acid Histidine, without Histidine, the bacteria will only survive with spontaneous back mutation, with a mutagen, the bacteria will have increased induce back mutations |
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What is two growth media used in the experiment? |
Minimal media without Histidine & Complete media with Histidine |
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What is the negative control? |
Water |
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What is the positive control |
Sodium azide is a known mutagen |
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What is the lab procedure? |
Soak paper disc in water, sodium azide, & unknown chemical, spread Salmonella culture on plates, place paper disc in center of plates, incubate at 37*C for 48 hours |
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What is the test results of complete media + disc w/water? |
Observation is zone of Inhibition is none, Normal growth of bacteria. Interpretation is water is not toxic to Salmonella, Control for viable growth of culture |
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What is the test results of Complete Media + disc w/Sodium azide? |
Observation is zone of inhibition is none, normal growth of bacteria. Interpretation is NaAz is not toxic to Salmonella, Control for viable growth of culture |
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What is the test results of Complete Media and disc w/test chemical |
observation is zone of inhibition and normal growth of bacteria. Interpretation is test chemical is toxic to Salmonella, control for viable growth of culture |
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What is the test results of Minimal Media + disc/water? |
observation is 4 colonies of Salmonella. Interpretation is normal spontaneous back mutations of bacteria. Control that bacteria will not grow in minimal media and spontaneous back mutations occur |
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What is the test results of Minimal Media + disc/Sodium Azide? |
observation is 10 colonies of Salmonella. Interpretation is number of colonies are above normal spontaneous back mutation to include additional induced back mutations. Control that bacteria will not grow in minimal media & NaAz (known mutagen) does cause induced back mutations |
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What is the test results of Minimal Media + disc/ test chemical? |
Observation is 2 colonies of Salmonella. Interpretation is normal spontaneous back mutations of bacteria with no induced back mutations. Test chemical is not a mutagen |
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How does the CM and MM plates differ? |
CM plate contains amino acid Histidine while MM plate does not contain Histidine |
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What does the CM plate tell you about the chemicals used in Ames test? |
The CM plate allows the Salmonella His- to absorb Histidine from media to use to produce proteins and live. Wate & NaAz are not toxic to Salmonella whereas the Test chemical is toxic |
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What does the MM plate tell you about the chemicals used in Ames test? |
The MM plate does not contain Histidine, so water represent normal spontaneous mutations, NaAz represents spontaneous and induced mutations and test chemical represents spontaneous mutations only. |
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What would we need to do to prove that any of the chemicals are human carcinogens? |
start with Ames test, positive results would include further testing on animals |
