Question

my research competitor heard about my brilliant evolution studies and decided to also pursue evolutionary studies in E. coli. She also inoculated 2 genetically identical populations to cells and has maintained these cultures for the past 15 years (population 1 and population 2). she has also noted a significant change in one of her populations in recent generations. In population 2, the cscR gene was duplicated in this population of cells (a second copy of the gene is now present on the bacterial chromosome). cscR is the sucrose operon repressor, the gene that codes for the repressor protein for the sucrose operon.

How might this duplication affect the functioning of this operon in the presence and absence of sucrose? provide rationale.

Do you predict that this difference in sucrose utilization will influence the evolutionary potential of this population? explain.

Answer 1

Please find the answers below:

Answer 1: According to the information, the new population has a duplicate copy of the cscR gene which is a repressor gene for sucrose operon. This means that expression of this gene will lead to accumulation of sucrose in the cells and thus the sucrose can be utilized as a carbon source for generation of energy. Hence, duplication of this gene will even enhance this operon effect and the sucrose metabolism will be highly regulated in these cells, making them dependent upon this only sugar for metabolism and survival.

Answer 2: As the dependency of these bacteria on sucrose will increase, their evolutionary trend will also enhance. This is because the mutant population has emerged in the culture after nearly a period of 15 years, thus a rondom mutation might have taken place which generated the metabolic difference. This makes the population highly plastic in reference to metabolism and evolution. If the sucrose is available in the growth medium appropriately, these cells would be able to survive for many generations and this random mutation will be established in the new population, hence evolve from the master strain.