Refer to the Graph Below, Containing Data from Three Assays

question 18

Multiple Choice

Refer to the graph below, containing data from three assays carried out simultaneously on a population of bacterial cells growing in culture.At various points in time, small samples of cells were taken from the population to measure cell number, total protein mass, and mass of enzymes involved in arginine biosynthesis.Halfway through the experiment, arginine was added to the medium in which the population was growing.A vertical arrow is shown on the graph to indicate this time. What do these data indicate about a mechanism of regulation of arginine biosynthesis in bacterial cells in response to high levels of available arginine?

• A) High levels of arginine stimulate a positive feedback regulatory mechanism.
• B) High levels of arginine stimulate a negative feedback regulatory mechanism.
• C) High levels of arginine stimulate an inhibition of gene expression.
• D) High levels of arginine stimulate an activation of enzyme covalent modification.
• E) High levels of arginine stimulate allosteric inhibition of arginine biosynthesis.

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Definitions:

Identical Medians

The statistical assessment that two or more groups have the same median value in their data distributions.

Identical Probability Distributions

Probability distributions that are exactly the same in terms of their statistical properties such as mean, variance, and skewness.

Single Population

Refers to a group or set of entities sharing one or more characteristics, from which data can be collected and analyzed as a unified whole.

Sign Test

A nonparametric test used to determine if there is a significant difference between paired observations.