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Simulating phase variation in Campylobacter VGEC: Answer sheet 1a.) No, you should have noticed that mutations occurred at different times, and different combinations of genes mutated to give different genotypes. There would have been differences in the number of cells capable of causing disease etc. This is because mutations are completely random events, and different combinations will be seen every time the simulator is run. This is reflected in nature. 2a.) The higher the mutation rate, the more cells capable of taking up movement, and sticking to host cells. 2b.) The population is more diverse at higher mutation rates. Fewer cells with the original genotype and few blocks of the same cells around each other. 3a.) Mutations that occur early have more impact. This is because mutations are passed down to descendant c Simulating phase variation in Campylobacter ells. The earlier this happens, the more likely the final population is to reflect this. 3b.) It is more likely that they will emerge from cells that already have one mutation. They can emerge from cells with zero mutations but this is unlikely. The different genes are independent from each other and the chance of all of them mutating at once is far higher! 3c.) There will be variation in the number of times the disease causing phenotype arises. This is because bacteria do not mutate towards favourable genotypes, they can just be selected for. This concept is also true for antibiotic resistance, cells do not mutate in response to antibiotics- resistant cells are just selected for by the drug. 4a.) RealisticThe simulator does display bacterial division, the random nature of mutation is also highlighted in the simulation. Genes do have different functions that can interact and contribute to bacteria causing disease. Unrealistic- Simulating phase variation in Campylobacter No selection (Disease would be favourable as it helps them to multiply), there are many more phase variable genes in real bacteria and their interactions are often more complex. The mutation rates in the simulator are too high and the bacterial populations are too small. There is no simulation of environmental factors which in real life would affect the speed of cell division. 4b.) The cost and time consumption of simulations are low, meaning you can do lots of repeats, generating lots of data. Key concepts conveyed by the activity Mutation is an entirely random process o Cells do not mutate towards a favourable genotype, the mutations are always there, they can just be selected for. Mutations generate diversity in populations of bacteria. Some of these mutations are preferable and help bacteria to cause disease.