Last month we mentioned the challenges of studying blue whales in a laboratory setting. If we want to know what a particular gene or protein does in an animal that large, we often have to rely on inference based on what a comparable gene or protein does in an animal we can study more readily like a mouse. And how do we know which protein is comparable–or homologous, to use the more technical term? Typically the search for homologous proteins starts with a sequence similarity scan, a check of an entire library of proteins from various species to see which have a large fraction of the same amino acids at the same locations. That’s straightforward enough when the match is at the level of 80%, but at just 20% similarity, it’s a bigger challenge–until now.
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