genetic drift

Examples of genetic drift in the following topics:

• Genetic Drift

  • Genetic drift is the change in allele frequencies of a population due to random chance events, such as natural disasters.
  • Genetic drift is the converse of natural selection.
  • Small populations are more susceptible to the forces of genetic drift.
  • Thus even while genetic drift is a random, directionless process, it acts to eliminate genetic variation over time.
  • Genetic drift in a population can lead to the elimination of an allele from that population by chance.

• Defining Population Evolution

  • Genetic variation in a population is determined by mutations, natural selection, genetic drift, genetic hitchhiking, and gene flow.
  • Five forces can cause genetic variation and evolution in a population: mutations, natural selection, genetic drift, genetic hitchhiking, and gene flow.
  • When selective forces are absent or relatively weak, gene frequencies tend to "drift" due to random events.
  • Even in the absence of selective forces, genetic drift can cause two separate populations that began with the same genetic structure to drift apart into two divergent populations.
  • Describe how the forces of genetic drift, genetic hitchhiking, gene flow, and mutation can lead to differences in population variation

• Gene Duplications and Divergence

  • Genetic divergence will always accompany reproductive isolation, either due to novel adaptations via selection and/or due to genetic drift, and is the principal mechanism underlying speciation.
  • Genetic drift or allelic drift is the change in the frequency of a gene variant (allele) in a population due to random sampling.
  • Genetic drift may cause gene variants to disappear completely and thereby reduce genetic variation.
  • When there are few copies of an allele, the effect of genetic drift is larger, and when there are many copies the effect is smaller.
  • Divergent evolution is usually a result of diffusion of the same species to different and isolated environments, which blocks the gene flow among the distinct populations allowing differentiated fixation of characteristics through genetic drift and natural selection.Divergent evolution can also be applied to molecular biology characteristics.

• Population Genetics

  • Population genetics is the study of the distributions and changes of allele frequency in a population.
  • When allele frequencies within a population change randomly with no advantage to the population over existing allele frequencies, the phenomenon is called genetic drift.
  • The smaller a population, the more susceptible it is to mechanisms such as genetic drift as alleles are more likely to become fixed at 0 (absent) or 1 (universally present).
  • Genetic drift and natural selection usually occur simultaneously in populations, but the cause of the frequency change is often impossible to determine.
  • Together, the forces of natural selection, genetic drift, and founder effect can lead to significant changes in the gene pool of a population.

• No Perfect Organism

  • Therefore, the process of evolution is limited by a population's existing genetic variance, the physical proximity of alleles, non-beneficial intermediate morphs in a polymorphic population, and non-adaptive evolutionary forces.
  • When a neutral allele is linked to beneficial allele, consequently meaning that it has a selective advantage, the allele frequency can increase in the population through genetic hitchhiking (also called genetic draft).
  • While natural selection selects the fittest individuals and often results in a more fit population overall, other forces of evolution, including genetic drift and gene flow, often do the opposite by introducing deleterious alleles to the population's gene pool.
  • It is simply the sum of various forces and their influence on the genetic and phenotypic variance of a population.

• Misconceptions of Evolution

  • This results in change in the population if the characteristics are genetically determined.
  • Evolution is defined more broadly as any change in the genetic makeup of a population over time.
  • Genetic drift, for example, is another mechanism by which evolution may occurs.
  • Genetic drift occurs when allelic frequency is altered due to random sampling.
  • It is evolution by chance, and the smaller the population, the more significant the effects on genetic distribution due to sampling error.

• Genome Reduction

  • Over evolutionary times, genomes tend to increase in size due to the accumulation of duplication of the genome and an increase in genetic elements .
  • This process seems to be dominated by genetic drift resulting from small population size, low recombination rates, and high mutation rates, as opposed to selection for smaller genomes.
  • In fact, as much as 90% of the genetic material can be lost when a species makes the evolutionary transition from a free-living to obligate intracellular lifestyle.

• Emergence of Viral Pathogens

  • Many viruses that were once benign later become pathogens through genetic change, which can occur by several mechanisms.
  • However, many viruses that were once benign later become pathogens through a genetic change, which can occur by different mechanisms.
  • One common evolutionary process whereby viral genes change over time is called genetic drift, where individual bases in the DNA or RNA mutate to other bases.
  • Two processes drive the antigens to change: antigenic drift and antigenic shift (antigenic drift being the more common).
  • Antigenic drift occurs in both influenza A and influenza B viruses.

• Etiology of Schizophrenia

  • While genetics, environment, neurobiology, and psychosocial stress contribute to schizophrenia, the exact cause of the disease is unknown.
  • Most researchers agree that both genetic vulnerability and environmental triggers must be present for the disease to develop.
  • However, the correlation between socioeconomic status and schizophrenia could also be explained by the "downward drift" theory.
  • This theory posits that because people with schizophrenia cannot hold a job or function well in society untreated, they "drift down" to a lower status.
  • Summarize the genetic, environmental, and neurological factors related to the development of schizophrenia

• A Microscopic View: Drift Speed

  • The drift velocity is the average velocity that a particle achieves due to an electric field.
  • The drift velocity vdis the average velocity of the free charges after applying the field.
  • The drift velocity is quite small, since there are so many free charges.
  • The carriers of the current each have charges q and move with a drift velocity of magnitude vd.
  • Relate the drift velocity with the velocity of free charges in conductors