Escherichia coli and Clostridium acetobutylicum are reported to be derived from a common ancestor. They have some similar, but not identical gene sequences. What is the best explanation for this difference in genetic coding?
A. The two species never diverged, but were discovered by two different scientists and given different names.
B. The two species are not closely related, but E. coli passed the similar gene sequences to C. acetobutylicum via horizontal gene transfer.
C. After the two species diverged, the similar gene sequences evolved through convergent evolution.
D. After the two species diverged, the genes accumulated random mutations that resulted in similar, but not identical gene sequences.
Answer: D
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