Scientists studying transcription in yeast (Saccharomyces cerevisiae) created an experimental strain thatproduced 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 ug/mL solution of amanitin
and recorded the maximum elongation rate of the mRNA (Figure 2).
Q. Identify the dependent variable in the experiments. Identify the control group missing from the second experiment. Justify the need for this control group in the second experiment.
Answers
Dependent variable: maximum elongation rate. Control groups: wild and experimental strains not treated with amanitin. They are important to see if the change in elongation rates depends on the amanitin inhibition or any other variable.
Before answering the question, let us first review a few concepts.
Control group
- The control group is used to identify any other factors influencing the results obtained in the study, apart from the modified variables of the treatment.
- Individuals of the control group are selected from the same population as the treatment group.
- These two groups are identical in all aspects except for the independent variable, which changes in the treatment group but remains constant in the control group.
Independent variable
- Refers to the variables that induce a response in another variable.
- It changes or is modified to analyze how it affects another variable.
- The researcher changes on purpose the independent variable to observe the response of the dependent variable.
Dependent variable
- Refers to the variable that depends on any change in the independent variable.
- It represents a quantity of something, and its value depends on how the independent variable is modified.
- The change in the dependent variable might be proportional or inversely proportional to the change in the manipulated variable.
Experiment 1:
- Scientists created an experimental strain that produced a modified RNA polymerase containing a single amino acid substitution.
- They determined the maximum elongation rate during transcription
→ with the modified RNA polymerase enzyme
→ without the modified RNA polymerase enzyme
(1)The dependent variable is themaximum elongation rate
Experiment 2:
Amanitin is a specific RNA polymerase inhibitor that binds to the RNA polymerase active site and inhibits transcription.
- wild-type and experimental strains were treated with amanitin
- the maximum elongation rate of the mRNA was recorded
(1) Thedependent variableis themaximum elongation rate
(2) The missing control groups arewild-type and experimental strains not treated with amanitin.
(3) The importance of including the control groups is to analyze if the change in the elongation rates depends on the amanitin inhibition or any other variable.
You can learn more about dependen / independent variables and control groups at,
Answer:
Explanation:
Hello!
The scientist created an experimental strain that produces a modified RNA polymerase with a single amino acid substitution. This mutation is supposed to change the elongation rate of the mRNA during transcription.
The dependent or response variable, is the one the researchers are interested in, meaning, are the characteristics that the researcher will pay attention to and measure during the experiment.
In this example, the researcher is interested in testing the max elongation rate during transcription, which is the dependent variable of this experiment.
In the second part of the experiment, both strains of yeast, wilds, and experimental, where exposed to 40ug/mL solution of amanitin and recorded the maximum elongation rate of the RNA. This is naturally to test the effects of amanitin over the elongation rate of the mRNA in both strains.
The control group is a set of experimental units that are exposed to the same conditions as the experimental groups, with the exception that they receive no treatment (or they receive a "no effective" treatment often called a placebo). The purpose of a control group is to know the natural response of the experimental units to a treatment-free environment, this way when comparing both groups, the researcher will be able to observe the differences or changes due to the applied treatments.
In the second experiment, there are missing two control groups, one made of the wild strain and the other made of the experimental strain, exposed to the same conditions as the treated strains.
I hope this helps!
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