Note that, experimentally, crossovers are only observable if they occur in a region that will produce a distinct daughter sequence. One crossover between a consecutive pair of variable positions will produce the same daughter sequence as 3, 5, 7, ... crossovers. Similarly 2, 4, 6, ... crossovers produce the same daughter sequence as no crossovers at all. In addition, any crossovers occurring between one end of the sequence and the first variable position are also unable to be detected by analysis of the daughter sequence.

Typically you will find the mean number of

In DRIVeR, you can choose to enter either the mean number of

Note also the following:

- The maximum
*observable*crossover rate is (*M*-1)/2, where*M*is the number of variable positions. If the*true*crossover rate is very high, then the variable positions will be essentially randomly assigned in each daughter sequence, and all possible daughters will be essentially equally likely (in fact you can use GLUE instead of DRIVeR).

- Since we assume that crossovers cannot occur immediately
following a variable position (due to the nature of the reassembly
reaction), if two variable positions are adjacent in the parent
sequences, then they will remain linked in all daughter sequences
and the number of possible daughter sequences and maximum
*observable*crossover rate will be reduced accordingly.

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