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In 1988 a scientist called Richard Lenski and his group used a single ancestral genome of *Escherichia coli* to put 12 genetically identical populations in 12 identical environments - VCE - SSCE Biology - Question 11 - 2023 - Paper 1
Question 11
In 1988 a scientist called Richard Lenski and his group used a single ancestral genome of *Escherichia coli* to put 12 genetically identical populations in 12 identi... show full transcript
Worked Solution & Example Answer:In 1988 a scientist called Richard Lenski and his group used a single ancestral genome of *Escherichia coli* to put 12 genetically identical populations in 12 identical environments - VCE - SSCE Biology - Question 11 - 2023 - Paper 1
Step 1
What effect would you expect this mutation to have on subsequent generations of this group of bacteria and why?
Answer
The mutation allowing the bacteria to utilize citrate as an energy source would likely result in an increased rate of reproduction among those carrying the mutation. This would enhance their competitive advantage, allowing them to reproduce more efficiently than those relying solely on glucose. Over subsequent generations, we could expect an increase in the frequency of the allele responsible for citrate metabolism within the population, driven by natural selection favoring this advantageous mutation.
Step 2
Describe how you would conduct an experiment to investigate the effect of different glucose concentrations on the frequency of the mutant citrate phenotype.
Answer
To investigate the effect of glucose concentrations on the mutant citrate phenotype, I would conduct an experiment by setting up several flasks, each containing the same volume of growth medium but varying concentrations of glucose (e.g., 0%, 1%, 2%, 5%, and 10%). I would ensure the initial population in each flask comes from the same generation after 30,000. Each flask would also contain an equal volume of citrate to maintain consistency. During each transfer every 24 hours, I would measure the growth and reproduction rates of the bacteria, as well as analyze the prevalence of the mutant phenotype using selective plating methods. This approach would allow for observations of how varying glucose levels influence both the growth rates and the phenotype frequencies of the population over time.