You have a leu auxotroph strain of e. coli. You suspect that if you mutagenize this strain, you can isolate prototrophic revertants. You irradiate these cells to generate mutants. A) What media should you plate these mutants on to identify leu prototrophs? answers: a. minimal media + carbon source b. minimal media - leu c. rich media d. rich media + ampicillin e. rich media -trp

You have a leu auxotroph strain of e. coli. You suspect that if you mutagenize this strain, you can isolate prototrophic revertants. You irradiate these cells to generate mutants. A) What media should you plate these mutants on to identify leu prototrophs? answers: a. minimal media + carbon source b. minimal media - leu c. rich media d. rich media + ampicillin e. rich media -trp

Biology: The Dynamic Science (MindTap Course List)

4th Edition

ISBN:9781305389892

Author:Peter J. Russell, Paul E. Hertz, Beverly McMillan

Publisher:Peter J. Russell, Paul E. Hertz, Beverly McMillan

Chapter15: From Dna To Protein

Section15.1: The Connection Between Dna, Rna, And Protein

Problem 1SB

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You are studying the tryptophan synthetase gene that Yanofsky also examined to determine the relationship between the nucleotide sequence and the amino acid sequence of the gene. Yanofsky found a large number of mutations that affected the tryptophan synthetase gene. A) If you took this mutant E. Coli line (that has an Arginine at this location) and exposed it to a mutagen that could potentially change bases, what are the second mutations you would most likely discover that would restore the activity of the tryptophan synthetase gene and where would it be located? B) Most of the mutations that Yanofsky recovered were missense mutations. However, Yanofsky also recovered a nonsense mutation that changed amino acid number 15 into a stop codon. This codon normally encodes Lysine. Does the recovery of this mutation support the hypothesis that this Lysine residue is critical in the function of the tryptophan synthetase protein?
Considering that prokaryote genomes do not have large introns, how is it possible to move a eukaryotic gene into a transformed bacterium, since they lack a spliceosome?
Let’s suppose you make a transposon library of the cellulose-secreting bacterium Komagataeibacter xylinus, with the goal of finding mutants that produce higher than normal amounts of cellulose, which would be useful industrially. However, despite your best efforts you are unable to isolate any transposon mutants that make more cellulose than the wild-type strain.Why might this have failed? List as many reasons as you can think of.
After mutagenesis of wild type Vibrio fisheri, you isolate two different mutant strains (A and B) that, unlike the wild type cells, fail to luminesce when grown to high density in a flask with appropriate medium. Curiously, however, when you inoculate both mutant strains in the same flask, you observe that the mixed (A+B) culture begins to emit light after growing dense. a) What gene/functions are likely affected in each of the two mutants? b) How does this explain their phenotypes?
Suppose that you I could obtain radioactively labeled penicillin. How could you use this compound to distinguish whether a penicillin-resistant bacterium harbors a gene encoding penicillinase or whether the bacterium has acquired a mutation in penA, penB, or mtr?
In this problem, just put the order of the intermediates on the pathway, starting with P and ending with Z and explain your reasoning. (So to get you started, notice the class 1 mutants—and there is only mutant in this class, which is mutant #5—won’t grow on minimal medium, but will grow if you give it substance Z. However, giving it substances, p, w, x, or y won’t help. This means that the gene that is mutated lies on the pathway in a place that the Z substances is to its right and all the other substances are to its left. The easiest next one to look at is the line with 2 pluses, and then the line with 3 pluses, and then the line with 4 pluses).
A research group is studying a bacterium X that binds to mucosal cells in the lung and invades. Wildtype X has an LD50 value of 10 bacteria when administered to mice by inhalation. Using transposon mutagenesis, the researchers have isolated two mutants of X that they call Xmut1 and Xmut2, both of which have LD50 values of 105 when inhaled by mice. However, in tissue culture cells, Xmut1 can invade the cells just as well as wild-type X, while Xmut2 cannot. Provide a possible explanation for these results.
In Hershey-Chase experiment, bacteriophages protein coats were tagged with radioactive isotope S-32. These phages were used to infect E. coli cells and the cells were further centrifuged to form pellets. Why was the radioactivity level of S-32 found greater outside the cells compared to the E. coli cell pellets? Explain briefly. If the experiment is repeated in the same manner but this time the phage protein coats are labelled with isotope X and the phage DNA with isotope Y, which isotope’s radioactivity will be found in greater amounts in the E. coli cell pellets after centrifugation? Explain briefly.
The genetic alteration responsible for sickle-cell anemia in humans involves: a transition mutation from A to G, substituting glutamic acid for valine in a-globin a transversion mutation from T to A, substituting valine for glutamic acid in b-globin a transition mutation from T to C, substituting valine for glutamic acid in b-globin a transversion mutation from G to C, substituting glutamic acid for valine in a-globin a frameshift mutation of one ATC codon, removing glutamic acid from b-globin
The reason why Beadle and Tatum observed four different categories of mutants that could not grow on media without methionine is because a. the enzyme involved in methionine biosynthesis is composed of four different subunits. b. the enzyme involved in methionine biosynthesis is present in four copies in the Neurospora genome. c. four different enzymes are involved in a pathway for methionine biosynthesis. d. a lack of methionine biosynthesis can inhibit Neurospora growth in four different ways.
Why can it be said that transcription of thebacteriophage T7 genome requires two enzymes?
"The molecule serving as the genetic material is expected to absorb at the wavelengths shown to be mutagenic." Explain this statement ?