Evaluate the effect of mutation, gene flow and genetic drift

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Evaluate the effect of mutation, gene flow and genetic drift on the gene pool of populations (ACSBL091, ACSBL092)

Effect of mutation on the gene pool of populations:

  • Mutation is the prime source of genetic variation and when mutations occur in germ cells, they become inheritable and will pass from the parent to the offspring.
  • Mutations are likely to either introduce new alleles with new traits or remove alleles thus eliminating a number of traits, resulting in increase or decrease of gene pool in a population.
  • Although mutations occur rarely, the probability of passing of a mutant gene from generation to generation depends on whether it is dominant, co-dominant, or recessive.
  • At times, mutation help organisms to survive. An ideal example is antibiotic resistant strains of bacteria. Mutation occurs in these bacterial species and once they are passed over to the next generations, a huge population of bacteria might become resistant to specific antibiotics.
  • Decrease in gene pool due to mutation may turn lethal and can cause extinction of a certain population because decrease in allele number in one population will gradually increase the possibilities of the same event to occur in the following generations and at some point, the population will not have enough variation to survive.

Effect of gene flow on the gene pool of populations:

  • Gene flow is the transfer of genetic variation from one population to another.
  • Though animals have more migrative capability as compared to plants, pollen and seeds may be carried great distances by animals or wind thus facilitating gene flow in plants as well.
  • Gene flow can bring new alleles into a population which occurred by chance and were successful in other populations accelerating microevolution.
  • Gene flows are mostly horizontal (transfer of genetic material in ways other than reproduction) and hybridization.
  • Gene flow can ensure fitness of population and increase the survival rate of a particular population.

Effect of genetic drift on the gene pool of populations:

  • Mechanism of evolution where allele frequencies in a population change due to chance.
  • In other words, Genetic drift is change in frequency of alleles due to "sampling error" in selecting the alleles for the next generation from the gene pool of the current generation.
  • Although genetic drift happens in populations of all sizes, its effects tend to be stronger in small populations because, the smaller a population is, greater are the chances of absolutely losing alleles in the process of evolution.

Extract from HSC Biology Stage 6 Syllabus. © 2017 Board of Studies NSW.