In biology, "genetic load" can mean a couple of things:
- The number of harmful genes maintained in a population.
- The amount by which the average fitness of the population is lowered due to the harboring of harmful genes (relative to the fitness it would have if an ideal genotype was common in the population).
The information in this writeup was taken from the science dictionary at http://biotech.icmb.utexas.edu/; I oversaw the development of the dictionary (the website was mothballed in 1998) and I believe I wrote the entry this is based on.