MICOBIOLOGY (BIOL. 33211) Assignment 3 (cont Name Student ID Date Section A: Gen

Question

MICOBIOLOGY (BIOL. 33211) Assignment 3 (cont Name Student ID Date Section A: Genetics 1. A hoth ciulture of his Salmonella ophimurium is inoculased onto an a plate ehan dopa ion several colonies are observed Explh(posible muilagems) have beem ded. Aer incubation, contain histidine. No other 2. A broth culture of his S. typhimm is inoculated onto an agar plate that does mutagenic chemical is added, but no evidence of mutations shows up after int: Review Step 1 of the Ames test procedure and consider at which stage histidine. A strongly Why? (Hint during the life cycle of a microbe a mutation would take place. The strain of his S. pphimurium is unable to make anyone ill, for it requires a histidine-rich environment for growth. Yet, extreme care should be taken to prevent contamination and potential infection when performing this test. Why? 3. 84

Explanation / Answer

1. Spontaneous mutation or back mutation occurs in the his synthesis gene. So, several colonies are visible in the plates.

2. Due to strong mutagenic chemical there is chance to get double mutation. After reversion his+ it again get mutated and comes down to his-.

3. If any contamination happen means there is a chance to become virulent form of s.typhi.
It require histidine to their normal growth, if any infection occurs to the lab students he bocome a host. In the host lot of histidine molecules are present so S.typhi will grow easily and brings serious illness to him.

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