00:01
So this question wants us to explain ames ' test, and this was a test developed by bruce ames, where special strains of bacteria are used to evaluate the immunogenic and associated carcinogenic potential of chemicals.
00:14
So histidine -negative bacteria, which are bacteria unable to produce the amino acid histidine, are grown in a medium without histidine.
00:23
Now, histidine is a proteogenic amino acid, so it's fairly essential.
00:31
For bacteria to grow.
00:33
And if bacteria are unable to produce histidine and are not given histidine in their media, then these bacteria would be unable to grow.
00:45
So only bacteria which mutate to become histine positive, which are able to produce histidine, can grow in the media.
00:52
In this way, this media without histidine is selective only for bacteria, which are capable of producing histidine.
01:11
So bacteria inoculated with a non -mutogenic chemical are not expected to mutate...