Genetic load

Genetic variation, which is generated by mutation, recombination and gene flow, can reduce the mean fitness of a population, both now and in the future. This ‘genetic load’ has been estimated in a wide range of animal taxa using various approaches. Advances in genome sequencing and computational techniques now enable us to estimate the genetic load in populations and individuals without direct fitness estimates. Here, we review the classic and contemporary literature of genetic load. We describe approaches to quantify the genetic load in whole-genome sequence data based on evolutionary conservation and annotations. We show that splitting the load into its two components — the realized load (or expressed load) and the masked load (or inbreeding load) — can improve our understanding of the population genetics of deleterious mutations. • Ohta, T. Slightly deleterious mutant substitutions in evolution. Nature 246, 96–98 (1973). • Haldane, J. B. S. The cost of natural selection. J. Genet. 55, 511 (1957). • Haldane, J. B. S. The effect of variation of fitness. Am. Nat. 71, 337–349 (1937). • Muller, H. J. Our load of mutations. Am. J. Hum. Genet. 2, 111–176 (1950). This work presents the first explicit use of the term ‘ genetic load’ with an explanation of the relationship between the mutation rate and load, and controversial speculation on the possible effects of relaxed selection in humans. • Crow, J. F. Some possibilities for measuring selection intensities in man. Hum. Biol. ...

genetic load The average number of a. input load, in which inferior b. balanced load, which is created by selection favouring allelic or genetic combinations that, by segregation and recombination, form inferior c. substitutional load, which is generated by selection favouring the replacement of an existing allele by a new allele. Originally called the ‘cost of Citation styles Encyclopedia.com gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA). Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list. Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia.com cannot guarantee each citation it generates. Therefore, it’s best to use Encyclopedia.com citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites: Modern Language Association The Chicago Manual of Style American Psychological Association Notes: • Most online reference entries and articles do not have page numbers. Therefore, that information is unavailable for most Encyclopedia.com content. However, the date...

The basic ideas of genetic load and the cost of natural selection are both from J. B. S. Haldane. In his early papers on natural selection (1924–1932), Haldane was concerned with both the dynamics and the statics of evolution. He emphasized that, although evolution depends on changes of gene frequency, nevertheless at any one time the population is in approximate equilibrium for most factors. Keywords • Natural Selection • Mutation Rate • Average Fitness • Gene Substitution • Genetic Load These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves. • Brues, Alice M.: The cost of evolution vs. the cost of not evolving. Evolution 18, 379–383 (1964). • - Genetic load and its varieties. Science 164, 1130–1136 (1969). • Chung, C. S.: Relative genetic load due to lethal and detrimental genes in irradiated populations of Drosophila melanogaster. Genetics 47, 1489–1504 (1962). • -, O. W. Robinson, and N. E. Morton: A note of deaf mutism. Ann. Hum. Genet. 23, 357–366 (1959). • Crow, J. F.: Some possibilities for measuring selection intensities in man. Human Biol. 30, 1–13 (1958). • - Population genetics. Amer. J. Hum. Genet. 13, 137–150 (1961). • - Population genetics: Selection. Methodology in human genetics. Ed. by W. Burdette. San Francisco: Holden-Day 1962. • - The concept of genetic load: A reply. Amer. J. Hum. Genet. 15, 310–315 (1963). • - Problems of ascertainment in the analysi...

Recent Examples on the Web In the proximate sense this purging of the genetic load occurs through human misery. — Razib Khan, Discover Magazine, 25 Aug. 2010 For example, how much of the Sub-Saharan genetic load in modern Egyptians is post-Roman, and how much pre-Roman? — Razib Khan, Discover Magazine, 17 Jan. 2011 In fact with plants selfing lineages achieve just this state of mutational perfection by exposing their recessive alleles and purging their genetic load (this seems less attainable with complex animals). — Razib Khan, Discover Magazine, 23 July 2012 These examples are programmatically compiled from various online sources to illustrate current usage of the word 'genetic load.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors.

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript. • Millions of new genetic variants have been discovered through sequencing studies and deposited in human genomic databases. Many of these, particularly rare variants, have been annotated as deleterious. • Recent research has examined whether different human populations have a varying burden of deleterious alleles — a concept referred to as mutation load. • Several recent studies have suggested that there is no significant difference among populations in the estimated number of deleterious alleles per individual. However, these analyses are sensitive to annotation prediction algorithms and summary statistics, leading to different, sometimes contradictory, interpretations. • These calculations also involved a number of simplifying assumptions, including additive allelic effects, no epistasis and simple distributions of selection coefficients across deleterious variants and across populations. • Following classical models of mutation load, we consider genotype frequencies in order to highlight how mutation load can change under different models of dominance. • Additionally, genetic drift has shifted the allele frequency spectrum of deleterious var...

Measure in population genetics Genetic load is the difference between the Fundamentals [ ] Consider n genotypes A 1 , … , A n where U is the total deleterious mutation rate summed over many independent sites. The intuition for the lack of dependence on the selection coefficient is that while a mutation with stronger effects does more harm per generation, its harm is felt for fewer generations. A slightly deleterious mutation may not stay in mutation–selection balance but may instead become High load can lead to a The accumulation of deleterious mutations in humans has been of concern to many geneticists, including Beneficial mutation [ ] In sufficiently genetically loaded populations, new beneficial mutations create fitter genotypes than those previously present in the population. When load is calculated as the difference between the fittest genotype present and the average, this creates a More recent "travelling wave" models of rapid adaptation derive a term called the "lead" that is equivalent to the substitutional load, and find that it is a critical determinant of the rate of adaptive evolution. Inbreeding [ ] Inbreeding increases Likewise, in a small population of humans practicing Recombination/segregation [ ] Combinations of alleles that have evolved to work well together may not work when recombined with a different suite of coevolved alleles, leading to Migration [ ] Migration load is the result of nonnative organisms that aren't adapted to a particular environme...