Mutational

The most important mutational changes affect the of the virus - its ability to infect a specific part of the body.

The trial also assessed how Tecentriq performed among patients with a "high tumor mutational burden," which means that they had high levels of genetic mutations in scraps of cancer DNA detected in blood tests.

As well, pancreatic tumors are particularly aggressive "due to a mutational profile that makes it resistant to therapies that work better for other tumor types," explained Dr. Angela Alistar.

Mutational burdens were higher among patients with a history of smoking, who comprised more than three-quarters of those in the study, and lower among those without an alteration of the gene EGFR.

Due to the ongoing production of mutant sequences, selection does not act on single sequences, but on mutational "clouds" of closely related sequences, referred to as quasispecies.

Ohno hypothesized that mammal genomes could not have more than 30,000 loci under selection before the "cost" from the mutational load would cause an inescapable decline in fitness, and eventually extinction.

Providing no mutational event occurs the resulting daughter cells are genetically identical to the original cell.