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Evolutionary Biology of Parasitism
Published in Eric S. Loker, Bruce V. Hofkin, Parasitology, 2015
Eric S. Loker, Bruce V. Hofkin
Microevolutionary studies are largely involved with monitoring changes in the distribution and frequency of genes in populations (Box 7.1) and with investigating the causes of those changes. You may recall that we have already discussed parasite populations both from the standpoint of being reservoirs of parasite diversity (Chapter 2) and from their complex structure (Chapter 6). Changes in the distribution and frequency of genes in populations are the essence of evolutionary change. Often changes in the abundance of variant forms (called alleles) of particular genes are followed over time by evolutionary biologists. Of particular interest is the extent to which basic evolutionary processes such as mutation, gene flow, genetic drift, and natural selection can combine to influence the degree of genetic variability within and among populations. The more populations become differentiated from one another, the more structure they are said to possess. Understanding the microevolutionary process and how it affects parasite populations is important because it helps us to gauge the evolutionary or adaptive potential of these populations. For example, how readily might a particular parasite population evolve drug resistance or withstand a control program? As we will see, what happens at the microevolutionary scale has considerable potential to impact macroevo-lutionary events such as speciation as well.
Setting the scene
Published in Jessica Mozersky, Risky Genes, 2012
Whereas natural selection presumes that beneficial alleles will increase in frequency over time, genetic drift is the random fluctuation in the frequency of a specific gene or allele in a population regardless of whether it is beneficial or not (Stone et al. 2007).1 According to genetic drift, there is always a possibility that a deleterious genetic mutation will survive randomly. Genetic drift is inversely related to population size so that in a small population genetic drift will have a stronger effect (Bamshad et al. 2004). If, for example, one member of a founding population carries a deleterious mutation but the founding population contains 1,000 members, then only 0.1 per cent of the total population carries the mutation and the effect is not particularly large. If, on the other hand, the founding population has only 10 members, then 10 per cent of the population is now affected with the mutation and so the ‘genetic drift’ has a much larger influence.
Stress memory in two generations of Plantago major from radioactive and chemical contaminated areas after the cessation of exposure
Published in International Journal of Radiation Biology, 2023
Nadezhda S. Shimalina, Vera N. Pozolotina, Natalya A. Orekhova
The development of short roots can be considered as plants’ adaptive trait to the HM-contaminated area. This trait was probably fixed in the population by the selection of resistant genotypes and persisted for three generations after the removal of toxic stress. The assumption of this selection is supported by the decrease in genetic diversity that we observed in P. major populations from the zone of influence of the KCS (Shimalina et al. 2020). It was shown by the case of Lychnis flos-cuculi that loss of genetic variability and high differentiation of plant populations under conditions of TM contamination of soils is associated with a founder or bottle-neck effect during recolonization of heavily contaminated areas or elimination of a significant part of populations under toxic load (Dulya and Mikryukov 2016). Interactions between selection, gene flow, and genetic drift can lead to local adaptation, a mechanism that helps maintain adaptive variability in cenopopopulations (Meyer et al. 2010).
Understanding the role of genetic susceptibility (ACE2 and TMPRSS2) in COVID-19
Published in Egyptian Journal of Basic and Applied Sciences, 2022
Abdullahi Tunde Aborode, Sherifdeen Bamidele Onigbinde, Khadijah Omoshalewa Sanusi, Noah Alaba, Aderinola H. Rasaq-Lawal, Babatunde Samuel Obadawo, Allison Olatoyosi, Saidat Omowunmi Adeniran-Obey, Victor Onwukwe, Uchenna Asogwa, Ridwan Iyanu Arinola, Seun Idowu Imani, Ayoola S. Fasawe, Ibukunoluwa Sodiya, Sherif Babatunde Adeyemi, Gaber El-Saber Batiha
The effect of different genetic variants among other populations occurs due to genetic drift [19]. Genetic drift occurs in diverse peoples, where there is the infrequent occurrence of alleles that face a chance of being lost. Once it starts, genetic drift will continue until the involved alleles are either lost by a population or are the only alleles present at a present or particular gene locus within a population [19]. Both possibilities decrease the genetic diversity of a person. Genetic drift can result in the loss of rare alleles and can reduce the size of the genetic pool. It also causes a new population to genetically district from its original population, which has led to the hypothesis that genetic drift plays a role in the evolution of more recent species [19].
Increased alcohol preference and intake in nicotine-preferring rats
Published in The American Journal of Drug and Alcohol Abuse, 2020
Baran Ozturk, Sakire Pogun, Lutfiye Kanit
Another limitation of the current study is the possibility of genetic drift. Our starting generation (F0) was 99 rats; of these, nicotine preferring and non-preferring rats were selected and outbred. As discussed in Crabbe et al. (80), our starting animal population was finite, rather than theoretically infinite as assumed for quantitative genetic models. Therefore inbreeding was practically unavoidable, possibly resulting in accidental fixing of trait-relevant and – irrelevant genes. Considering our starting population of 99 animals and the relatively long selective breeding period, genetic drift could have occurred making it difficult to separate allelic differences due to the phenotype being selected and those that are unrelated to the phenotype (81).