2 You are studying regulation of the yeast enzyme glutamine synthetase (GS), which is encoded by the GLN1 gene. You have isolated two mutants, designated gln2– and gln3–, that give decreased GS activity. Mating of either gln2– or gln3– haploids to wild type produces heterozygous diploids that show normal amounts of GS expression. When you cross either a gln2– or gln3– haploid to a gln1– strain the resulting diploids show normal expression of GS, that could explain the effect of the gln2– and gln3– mutations on the regulation of GLN1.

The GLN1 gene shows a rather complex regulation in response to different amino acids. When either glutamate (glu) or glutamine (gln) is added to the medium, the amount of GS expression diminished and when both glutamate and glutamine are added to the medium GS expression is shut off completely. The effects of different mutants on the response to glu and gln are shown below.

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Which of the following is characteristic of the events occurring at an excitatory synapse?

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#Question id: 11126

#SCPH28 | Zoology

Which of the following is characteristic of the events occurring at an excitatory synapse?

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#Question id: 11127

#SCPH28 | Zoology

As the receptor potential rises higher above threshold, which of the following best characterizes the new frequency of action potentials?

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Inhibition of pain signals by tactile stimulation of a skin surface involves which of the following selections?

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#Question id: 11128

#SCPH28 | Zoology

Inhibition of pain signals by tactile stimulation of a skin surface involves which of the following selections?

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#Question id: 11129

#I Life Science/ Life Sciences Group – I-V

Which of the following statements concerning the neuronal membrane at rest is correct?