Scientists studying transcription in yeast (Saccharomyces cerevisiae) created an experimental strain that produced a modified RNA polymerase containing a single amino acid substitution. The scientists determined the maximum elongation rate during transcription with and without the modified RNA polymerase enzyme (Figure 1 ).

The compound amanitin, which is commonly found in toxic mushrooms, is a specific RNA polymerase inhibitor. Amanitin binds to the RNA polymerase active site and inhibits transcription. In a second experiment, the scientists treated the wild-type and experimental strains of S. cerevisiae with a 40 μg/mL solution of amanitin and recorded the maximum elongation rate of the mRNA (Figure 2 ). Error bars represent ±2SEx¯ .

Identify the dependent variable in the experiments. Identify a control group missing from the second experiment. Justify the need for this control group in the second experiment.

elongation rate of strain of S.cerevisiae during transcription.

wild-type and experimental strain not treated with soultion of amanitin will be the control group. The elongation rate of mRNA of this group must be observed.

Explanation:

Dependent variable is one whose value depends on another value. Here effect of presence of mRNA polymerase enzyme and inhibtor on elnogatino rate of mRNA is being observed. So elongation rate is the dependent variable

Control group is one where independent variable whose effect is being observed can't influence the results. In experiment 2, the effect of inhibitor is being observed. So the control group must not have that inhibitor. Other conditions must remain same for experimentan and control group.

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