If the inducer [allolactose] is present in the negative control then it will bind to the repressor decreasing its ability to bind to the operator due to which the transcription begins again and the operon is turned on.
Lac Operon is a set of three genes z, y & a which are regulated under the same promoter which regulates the amount of lactose production in the cell.
An inducer is a molecule that has the ability to induce or activate the operon. ex- in the case of the lac operon, allolactose acts as an inducer.
A repressor is a molecule that will repress or restricts the transcription of the genes of the operon, as a result, the operon will be switched off.
When the lac operon is under negative control, with no CAP [catabolite repressor protein] binding activity, the repressor remains active and thus binds to the operator region of the operon, as a result, no transcription takes place and the operon will be switched off.
But if the inducer will be present even in the negative control then the transcription takes place and the operon will be on.
Learn more about lac operon here
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Answer: The correct answer is -
D) giraffes having increasingly longer necks over time.
Natural selection is an evolutionary mechanism that was proposed by Darwin.
According to this mechanism, organisms that are better capable of adapting to their changing environmental conditions, survive and increase their number through reproduction whereas other are eliminated from the population.
Example - Long neck of Giraffe, which is much elongated, lofty stature, that was beautifully adapted for browsing on the higher tree branches. This was an adaptation with slow and gradual change in the gene frequency as the lower vegetation was eaten by other animals. Due to this, giraffes had to search for other source (that was higher tree branches).
This is considered as a peculiar example of natural selection.
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Answer:Independent Variable
A variable that you (the scientist) changes and you have control over. The factor being tested in an experiment.
Dependent Variables
Factor(s) that change in response to other factors. It's what your measuring in your experiment to see whether or not the independent variable made an impact. This is what the scientist focuses their observations.
Explanation:
