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You use replica plating to isolate a culture of an E. coli auxotroph, unable to grow without tryptophan, from a culture of prototrophs. For a number of months, you propagate your tryptophan auxotroph culture on GSA (glucose salts agar) medium supplemented with tryptophan. One day, you mistakenly transfer some of your strain onto a new GSA plate that does not contain tryptophan. You realize your mistake after you have left the lab for the day and it is too late to correct it. However, when you return following 24 hours of incubation, you discover a few colonies of E. coli growing on the GSA medium. Please explain this result: why were you able to originally obtain a tryptophan auxotroph from a prototroph culture, and why months later did you find E. coli growth on GSA lacking tryptophan?

The term Speech Awareness Threshold is synonymous with ________.

What do cartilaginous (ex. skarks) and bony fishes have in common?

Which of the following traits most contributed to the evolutionary success and diversification of insects?

Animals classified as Ecdysozoans share which of the following characteristics?

Members of the subphylum Chelicerata, such as spiders and scorpions, are characterized by…

Which of the following groups is most closely related to vertebrates?

Which tuning-fork test compares air and bone conduction within the same ear?

Word recognition testing is typically conducted at ____________ dB above SRT

Consider the experiment of taking this exam. Suppose we model your score for this exam as Y=5X, where X is a discrete uniform random variable over {0,1,…,N}, and N is the total number of questions. Note that X represents a random variable which is the total number of questions you get right. Find