You are a college professor running a systematics lab.  Your…

You are a college professor running a systematics lab.  Your grad student found a paper in the literature reporting the phylogeny of her favorite group of organisms, based on gene A.  To verify the published phylogeny, she sequences gene B and gets a slightly different phylogeny.  What are four possible explanations for the difference between her result and the published one?

The tree below was estimated from HIV viral sequences for th…

The tree below was estimated from HIV viral sequences for the purpose of determining whether nurse (N2) infected a patient (P) with HIV-AIDS.  The tree also includes viral sequences from a number of other infected individuals (“RO”) from the same region.  Based just on this tree what should you conclude?