"Though millions of mutations in the target gene are believed to have occurred, only about 700 of those were capable of creating a new variant of the target gene. In all, the researchers identified 343 unique strains, each of which contained one of just six variants of the critical gene."
Millions or 20 million. Estimate or guesstimate?
The conclusion reached by the researchers seems to be that " "The duplicate study suggests that the pathways of molecular adaptation are reproducible and not highly variable under identical conditions," Shamoo said.
Why?
Estimate based upon known rates.
The conclusion reached by the researchers seems to be that " "The duplicate study suggests that the pathways of molecular adaptation are reproducible and not highly variable under identical conditions," Shamoo said.
Why?
Proteins will not have an infinite number of useful sequences at any particular set of conditions. Many of the point mutations that occurred will not have caused any change in the protein sequence due to codon redundancy. Other point mutations will cause sequence change that is neutral and likely to be lost through genetic drift. Others will cause sequence change that is detrimental. They found the few beneficial point mutations that make the protein more effective under the specific conditions tested.
It is like when you get in your car to drive to work there are hundreds of routes you could take, but probably only a couple that get you there in good time.