Introduction to Population and Evolutionary Genetics

Factors that Affect Stability of Gene Frequencies

Mutation

• Classified as beneficial, harmful or neutral
• Can occur by point mutations (changes in a single nucleotide) or small insertions or deletions of the nucleotide sequence.
• Harmful mutations are lost if they reduce fitness
• If fitness is improved by a mutation, then the frequency of that allele will increase from generation to generation
• The mutation could be a change in one allele to resemble one currently in the population, for example from a dominant to a recessive allele.
• The mutation could generate an entirely new allele.
  • Most of these mutations though will be detrimental and lost.
  • If the environment changes, the new mutant allele may be favored and eventually become the dominant alelle in that population.
  • If the mutation is beneficial to the species as a whole, migration must occur for it to spread to other populations of the species.
• Gene duplication favor mutational events.
  • The duplicated gene can undergo mutations to generate a new gene that has a similar, but a slightly modified function for the organism.
  • This type of evolution generates multigene families. (Examples: hemoglobin and muscle genes in humans, and seed storage and photosynthetic genes in plants)