Genetic markers

Genetic load is a concept in population genetics that measures the relative decrease in the mean fitness of a population due to the presence of genetically deleterious alleles. It was first introduced by the geneticist J.B.S. Haldane in 1957.

Definition

The genetic load of a population is defined as the difference between the fitness of an idealized organism that has the optimal genotype at all loci in the genome, and the fitness of the average organism in the population. Genetic load can be caused by several factors, including mutation, selection, and genetic drift.

Types of Genetic Load

There are three main types of genetic load: mutation load, segregation load, and substitution load.

Mutation Load

Mutation load is the decrease in fitness caused by new, deleterious mutations. It is a measure of the cost of mutation rate to the fitness of the population.

Segregation Load

Segregation load is the decrease in fitness caused by the presence of deleterious alleles that are maintained in the population by heterozygote advantage. This occurs when the heterozygote has a higher fitness than either homozygote.

Substitution Load

Substitution load is the decrease in fitness caused by the substitution of deleterious alleles for beneficial ones. This can occur due to genetic drift or gene flow.

Measurement of Genetic Load

The measurement of genetic load is complex and can be done using several methods, including quantitative genetics and molecular genetics. The measurement of genetic load is important for understanding the evolutionary dynamics of populations and for predicting their future evolutionary trajectories.

Implications of Genetic Load

The concept of genetic load has important implications for conservation biology, evolutionary biology, and medical genetics. In conservation biology, high genetic load can increase the risk of extinction for small populations. In evolutionary biology, genetic load can influence the rate of evolution and the maintenance of genetic variation. In medical genetics, genetic load can contribute to the burden of genetic disease in human populations.

See Also

• Genetic drift
• Fitness (biology)
• Population genetics
• Mutation
• Selection

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