||"As far as quantitative estimates of mutation rate are
concerned, a large fraction of them have been obtained
in recent studies that use a multigeneration direct
sequencing approach (table 1)." "As powerful as direct sequencing may be, it has not yet reached a level of economy to be able to answer all fundamental questions pertinent to mutation rates. The four recent studies that involved direct sequencing have yielded very few mutations: four in the human pedigree (Xue et al. 2009), 35 in Saccharomyces cerevisiae (Lynch et al. 2008), 37 (Haag-Liautard et al. 2007) and 174 (Keightley et al. 2009) in D. melanogaster and 30 in Caenorhabditis elegans (Denver et al. 2004). Although some qualitative observations on different kinds of mutations have been made in some of these studies (table 1), obviously, to be of use for refining this knowledge on a quantitative level, the amount of data must increase by more than an order of magnitude. Nevertheless, it may be useful to define a set of unanswered fundamental questions pertaining to the study of mutation rates that may yet be tackled with the advance of cheaper sequencing."