Causes of molecular convergence and parallelism in protein evolution

To what extent is the convergent evolution of protein function attributable to convergent or parallel changes at the amino acid level? The mutations that contribute to adaptive protein evolution may represent a biased subset of all possible beneficial mutations owing to mutation bias and/or variation in the magnitude of deleterious pleiotropy. A key finding is that the fitness effects of amino acid mutations are often conditional on genetic background. This context dependence (epistasis) can reduce the probability of convergence and parallelism because it reduces the number of possible mutations that are unconditionally acceptable in divergent genetic backgrounds. Here, I review factors that influence the probability of replicated evolution at the molecular level

Demonstration of Epstein-Barr virus DNA in a previously healthy boy with fulminant hepatic failure

A previously healthy 9-year-old boy died from acute liver failure during an acute Epstein-Barr virus infection. Epstein-Barr virus DNA could be demonstrated in the liver by Southern blot--and by in situ hybridization techniques. The identification of the virus in the liver suggests a causal relation between the Epstein-Barr virus and the acute massive liver cell necrosis