In a nutrient medium that lacks histidine, a thin layer of agar containing around 10^9 Salmonella typhimurium histidine auxotroph produces around 13 colonies over a two day incubation period at 37 degrees centigrade. How do these colonies arise in the absence of histidine? The experiment is repeated in the presence of 0.4 micrograms of 2-aminoanthracene. The number of colonies the number of colonies produced over 2 days exceeds 10,000. What does this indicate about 2- anthracene? what can you surmise about its carcinogenicity?

We can conclude that colonies were able to grow in the absence of histidine due to reverse mutations that enabled the colony to synthesize histidine for its survival. Regarding 2-aminoanthracene, we can see that it induces mutations in an environment, which can be related to a high potential for carcinogenicity.

Explanation:

Reverse mutations can also be called suppressor mutations and occur when a mutation restores a number of genes that were disabled in an organism, for some reason.

According to the action of 2-aminoanthracene shown in the question above, we can conclude that it is a compound that induces mutations, so it was used in the culture medium with no histidine to stimulate reverse mutations in colonies, so that they would grow in that medium culture and synthesize the histidine itself.

However, we must note that a cancer can be developed through mutations. If 2-aminoanthracene is a mutagenic agent, we can consider it an agent with high carcinogenicity.

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many other transport proteins, often called pumps, move materials against a concentration gradient. active transport drives molecules across a membrane from a region of lower concentration to a region of higher concentration. this process, shown in figure 5.1, uses transport proteins powered by chemi- cal energy.