The extracellular glucose inhibit transcription of the lac operon (D) by reducing the levels of intracellular cAMP.
Lac operon is the assembly of various genes that are involved in the uptake and metabolism of lactose of E. coli or any other bacteria. It consists of a regulator gene, promoter gene, operator and structural gene. Structural genes are three: z, y and a. Each codes for a different enzyme.
cAMP is the cyclic Adenosine Monophosphate. It is produced by the bacteria when there are low levels of glucose in it. Hence it is also named as hunger signals. Therefore, cAMP is responsible for activating the operon to produce lactose.
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Answer:
Genetic drift
Explanation:
Genetic drift is defined as the random change in allelic frequencies from one generation to the other.
Genetic drift is an evolutionary mechanism in which the allelic frequencies in a population change through many generations. Its effects are harder in a small-sized population, meaning that this effect is inversely proportional to the population size. Genetic drift results in some alleles loss, even those that are beneficial for the population, and the fixation of some other alleles by an increase in their frequencies. The final consequence is to <u>randomly</u> fixate one of the alleles. Low-frequency alleles are the most likely to be lost. Genetic drift results in a loss of genetic variability within a population.
Genetic drift has important effects on a population when this last one reduces its size dramatically because of a disaster -bottleneck effect- or because of a population split -founder effect-.
Bacteria that change nitrogen gas from the atmosphere into solid nitrogen usable by plants are called nitrogen-fixing bacteria. These bacteria are found both in the soil and in symbiotic relationships with plants.
