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.

• Vestigial Structures

  • If there are no selection pressures actively lowering the fitness of the individual, the trait will persist in future generations unless the trait is eliminated through genetic drift or other random events.

• Reproductive Isolation

  • Given enough time, the genetic and phenotypic divergence between populations will affect characters that influence reproduction: if individuals of the two populations were to be brought together, mating would be improbable, but if mating did occur, offspring would be non-viable or infertile.
  • Reproduction with the parent species ceases and a new group exists that is now reproductively and genetically independent.
  • Over time, the forces of natural selection, mutation, and genetic drift will likely result in the divergence of the two groups .
  • The two species can live in close proximity, but because of their different soil preferences, they became genetically isolated.

• Hardy-Weinberg Principle of Equilibrium

  • The genetic variation of natural populations is constantly changing from genetic drift, mutation, migration, and natural and sexual selection.

• Evidence of Evolution

  • Evidence of a common ancestor for all of life is reflected in the universality of DNA as the genetic material, in the near universality of the genetic code, and in the machinery of DNA replication and expression.
  • For example, it is clear that the evolution of new functions for proteins commonly occurs after gene duplications that allow the free modification of one copy by mutation, selection, or drift (changes in a population's gene pool resulting from chance), while the second copy continues to produce a functional protein.