General features and properties of insertion sequence elements

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Impact of is on genome evolution - The importance of time scale.

ISs have had an important impact on genome structure and function. Several of these effects are considered in the following sections. In this context it is useful to understand the time scales involved in these processes since they are often confounded. Evolutionary time is used to compare species (106 years), historical time in comparisons within or between populations (102 - 104 years), variety time in selection experiments (1 - 102 years), and laboratory time for ongoing events such as experimental measurement of transposition frequencies or in biochemical analyses (10-3 - 1 years) (Alan Schulman, pers. comm.). Thus a "burst" of transposition in evolutionary time is many orders of magnitude longer than a "burst" of transposition in experimental biology.