A wild-type culture of haploid yeast is exposed to ethyl metha...

Question

A wild-type culture of haploid yeast is exposed to ethyl methanesulfonate (EMS). Yeast cells are plated on a complete medium, and 6 colonies (colonies numbered 1 to 6) are transferred to a new complete medium plate for further study. Four replica plates are made from the complete medium plate to plates containing minimal medium or minimal medium plus one amino acid (replica plates numbered 1 to 4) with the following results:

Identify the colonies that are prototrophic (wild type). What growth information leads to your answer?

Diagram showing yeast colonies on a complete medium and their transfer to replica plates with varying minimal media conditions.

Identify the colonies that are prototrophic (wild type). What growth information leads to your answer?

Accepted Answer

Welcome back, everyone. Let's look at our next question In an experiment. A microbiologist wanted to investigate the proto trophic and oxo trophic characteristics of five bacterial colonies. The colonies were isolated on a complete medium and then transferred to a mineral medium to identify their nutritional requirements. After incubation, the microbiologist observed that Colony one grew on the minimum medium While Colonies 2, 3 and four did not grow, Colony of five grew on the minimal medium supplemented with methionine. But our question says, which of the following colonies are proto trophic and what nutritional requirements do they have? Well, let's just recall before we go through our answer, choices that bacteria that are proto can synthesize their own essential nutrients. While bacteria that are oxo trophic lack the ability, Lack the ability to synthesize one or more essential nutrients. So with that in mind, let's look through our answer choices. A says Colony one is proto prophic and does not require any nutritional supplementation. Well, this is correct. Uh Colony one grew on minimal medium, which is medium that doesn't have any additional essential nutrients added to it. So that means that we know that colony one is proto tropic. And that means it can synth since it can synthesize all of its own essential nutrients. Doesn't there's no need of any further supplementation. I'm going to mark it with a little dot To say that it's correct. But wait to select it as our answer until we look at our other choices just to make sure there's nothing else that would be a better choice Choice. B says Colony five is proto trophic and requires methionine. Well, colony five does require methionine since it grew on minimal medium supplement with my methionine. But that means it's not proto trophic since it means something that means it's oxo trophic. So choice B is not correct. Then colony C says, excuse me, choice C says both colonies one and five are protropin and require methionine. Well, this is not correct As we know. Colony one Does not require methionine. Colony five is not proto trophic. So C is not our correct answer. And then Chote says none of the colonies are proto well, this is not correct since colony one is, if none of them were prophic, nothing would have grown on the plate with minimal medium. So we'll go back to that choice A and circle it since we, that's the best answer we found and recall which of the following colonies are proto tropic and what nutritional requirements do they have choice? A colony one is proto tropic and does not require any nutritional supplementation. See, you in the next video.

Key Concepts

Prototrophy vs. Auxotrophy

Minimal Medium

Replica Plating

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