Genetic Algorithms (GAs) toolbox is available when we install Matlab, but some cases need special treatment to our system. It may be related to constraint, and may be combination to other algorithms. Some students when doing their thesis or project need some manipulations to the algorithms. There are many books give additional source code for GAs. But the main source for me is an internet. We can find a lot of source code in Matlab by using a simple google. For example sivanandam in his book give a code in matlab but there are so many additional script that must be available first in order to make our code running well. One site that may be important to GAs user is here. One simple GAs may be need some m-file scripts like this.
Of course you can just type “optimtool” in command window, and choose GAs as your basis of optimization. But understanding something inside it I think very important, how selection, crossover, etc. so we can manipulate them for giving better efficiency, accuracy and speed.