There are two basic methods of
reproduction, called mutation and crossover:
Randomly change one or more digits in the string representing an
individual. For example, the individual 1-2-3 may be changed to
1-3-3 or 3-2-3, giving two new offspring. How often to do mutation,
how many digits to change, and how big a change to make are adjustable
parameters. 
Randomly pick one or more pairs of individuals
as parents and randomly swap segments of the parents. For example,
the individuals 1-3-3 and 3-2-3 may be chosen as parents. Suppose we
select a crossover point after the first digit, then the above will
generate two offspring: 3-3-3 and 1-2-3. As another example,
given two parents 1011010 and 1100010, if the crossover point is
between the third and fourth digits, then the two offspring are
1010010 and 1101010. The rate of crossover,
the number of parent pairs, and the crossover point(s) are adjustable
parameters. 
