AGB 121: Principles of Animal Genetics and Population Genetics (2+1)

BACKWARD MUTATION

The mutation from a mutant phenotype back to the original wild type phenotype is referred to as Back mutation, Reverse mutation or Reversion.

Genetic Suppression

• The effect of a mutation on the phenotype can be reversed, so that the original wild type phenotype is brought back. This reversal may be due to True Reversion or Suppression.
• Reversion may occur in two different ways.
• Restoration of the original phenotype may occur by
  • True Reversion
    • The mutation from a mutant phenotype back to the original wild type phenotype is referred as Back Mutation, Reverse Mutation or Reversion.
    • In a true reversion there is a reversal of the original genetic change.
  • Suppression
    • In suppression a change at a different site brings about phenotypic correction of the mutation.
    • In Suppression mutation, the occurrence of a second mutation at a different location in the genome, brings about phenotypic correction or compensation for the first mutation.
    • Suppressor mutations may occur at distinct sites in the same gene as the original mutation or in different genes or even in different chromosomes.
    • Suppression mutations are of two types,
      • Intragenic suppression and
      • Extragenic or Intergenic suppression.
    • In intragenic suppression a mutation in a gene is suppressed by another mutation in the same gene.
    • In intragenic suppression a mutation in a gene is suppressed by another mutation in the in different gene of the same chromosome or even in another chromosomes gene.

Suppressor genes

• Genes which suppress the activity of other mutated genes are called suppressor genes.