Question

What might be one explanation for the difference in the growth rate of the strains when the sugar source changes in a growth medium?

1) Different sugars can act as effector or repressor molecules in various strains, promoting or inhibiting transcription of genes depending on the type of sugar present.
2) Operons for anabolic pathways are controlled by many global regulatory mechanisms, and different sugars can favor initiation of different pathways depending on the strain of yeast.
3) All of the choices are correct.
4) Catabolic repression strategies of operons for using different sugars may vary among strains, thereby favoring initiation of transcription in one strain over another depending on the sugar.

Answer 1

The difference in growth rates when the sugar source changes is due to different regulatory mechanisms controlling gene transcription, with sugars like lactose or glucose triggering specific transcription responses like activation or repression through effector and repressor molecules.

Step-by-step explanation:

An explanation for the difference in the growth rate of the strains when the sugar source changes in a growth medium could be due to the distinct regulatory mechanisms that control transcription of genes related to sugar metabolism. Different sugars may act as effector or repressor molecules, influencing transcription either by promoting or inhibiting it, depending on the type of sugar present.

This is because operons, like the lac operon, utilize inducible and repressive controls to modulate the transcription of genes responsible for sugar metabolism. Moreover, catabolic repression strategies may also vary among strains, which can result in preferences for initiating transcription with one sugar over another.

In the case of the lac operon, when glucose levels are low, the cAMP-CAP protein complex serves as a positive regulator to induce transcription.

However, this transcription only occurs if lactose is present and glucose is absent. This is a clear example of how different sugars in the environment can unleash different regulatory mechanisms, causing variable growth rates among different bacterial strains when the sugar source changes.