genetic load The average number of lethal mutations per individual in a population. Such mutations result in the premature death of the organisms carrying them. Three main kinds of genetic load may be recognized:
a. input load, in which inferior alleles are introduced into the gene pool of a population either by mutation or immigration;

b. balanced load, which is created by selection favouring allelic or genetic combinations that, by segregation and recombination, form inferior genotypes every generation; and

c. substitutional load, which is generated by selection favouring the replacement of an existing allele by a new allele. Originally called the ‘cost of natural selection’ by the geneticist J. B. S. Haldane, substitutional load is the genetic load associated with transient polymorphism. The term ‘genetic load’ was originally coined by H. J. Muller in 1950 to convey the burden that deleterious mutations provide, but it is probably better recognized as a measure of the amount of natural selection associated with a certain amount of genetic variability, which provides the raw material for continued adaptation and evolution.

genetic load The average number of lethal mutations per individual in a population. Three main kinds of genetic load are recognized: (a) input load, in which inferior alleles are introduced into the gene pool of a population either by mutation or immigration; (b) balanced load, which is created by selection favouring allelic or genetic combinations that, by segregation and recombination, form inferior genotypes every generation; and (c) substitutional load, which is generated by selection favouring the replacement of an existing gene by a new allele. Originally called the ‘cost of natural selection’ by the geneticist J. B. S. Haldane, substitutional load is the genetic load associated with transient polymorphism. The term genetic load’ was originally coined by H. J. Muller in 1950 to convey the burden that deleterious mutations provide, but it is probably better recognized as a measure of the amount of natural selection associated with a certain amount of genetic variability, which provides the raw material for continued adaptation and evolution.

genetic load The average number of lethal mutations per individual in a population. Such mutations result in the premature death of the organisms carrying them. Three main kinds of genetic load may be recognized: (a)input load, in which inferior alleles are introduced into the gene pool of a population either by mutation or immigration;(b)balanced load, which is created by selection favouring allelic or genetic combinations which, by segregation and recombination, form inferior genotypes every generation; and(c)substitutional load, which is generated by selection favouring the replacement of an existing allele by a new allele. Originally called the ‘cost of natural selection’ by the geneticist J. B. S. Haldane, substitutional load is the genetic load associated with transient polymorphism. The term ‘genetic load’ was originally coined by H. J. Muller in 1950 to convey the burden that deleterious mutations provide, but it is probably better recognized as a measure of the amount of natural selection associated with a certain amount of genetic variability, which provides the raw material for continued adaptation and evolution.

genetic load The concentration of deleterious genes carried within a population.