A, B and C are three cross-hybridising genes in the human genome. In the mouse and frog genomes there is just one copy each of this gene: M and X respectively. You have sequenced the same 10000 bp open reading frame from each of these genes and the number of base pair differences between different pairs are as follows: A vs B=300 bps, B vs C=10 bps, A vs C=300 bps, A vs M=600 bps and A vs X=3000 bps. Assuming a constant rate of evolution with all members of this gene family and that mice and humans evolved apart 60 million years ago: HOW LONG AGO DID FROGS SPLIT FROM THE LINE LEADING TO MICE?

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