9.) You have isolated 7 conditional mutants for compound X. The results shown in
ID: 164751 • Letter: 9
Question
9.) You have isolated 7 conditional mutants for compound X. The results shown in the following table were obtained when the 7 mutants were analyzed for complementation. (+) indicates growth and a “0” indicates no growth when screened on minimal media. (4 pts)
Mutants
1
2
3
4
5
6
7
1
0
(+)
0
(+)
(+)
(+)
(+)
2
0
(+)
0
(+)
(+)
0
3
0
(+)
(+)
(+)
(+)
4
0
(+)
(+)
0
5
0
0
(+)
6
0
(+)
7
0
a.) How many different genes would have been defined?
b.) Which mutations are in the same gene?
10.) Explain how the Ames test can be used to detect potential mutagens? What are the limitations of this test?
Mutants
1
2
3
4
5
6
7
1
0
(+)
0
(+)
(+)
(+)
(+)
2
0
(+)
0
(+)
(+)
0
3
0
(+)
(+)
(+)
(+)
4
0
(+)
(+)
0
5
0
0
(+)
6
0
(+)
7
0
Explanation / Answer
B) mutations 1/3, 2/4, 4/7 and 5,6 are in same gene. 0 means appearance of mutant phenotype due to the mutations are in different allele of the same gene.
A) there are 3 different gene. Mutation in a different gene so appearence of wild type phenotype.
10. Ames test is used to detect mutagen. The bacterium used in this test is salomonella typhimurium that carries a defective gene making it unable to synthesize the amino acid histidine from the ingredient in culture medium. A suspension of histidine requiring strain of S. typhimurium has been plated with a mixture of a rat liver enzyme on agar lacking histidine. This disk of filter paper impregnated with 10 ug of 2- aminofluorene, a known carcinogen. This mutagenic effect of chemical has caused many bacteria to grow without histidine, forming the colonies seen around the disk.
Limitation
This S. Typhimurium is not a perfect model for human body.
Some substances that cause cancer to lab animal do not give a positive ames test.
Some substances mutagenic for the bacteria used in his test may also turns out to be a carcinogen that is cause cancer.
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