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

TISSUE OF ORIGIN

• On the basis of the type of cells in which mutations occur, there are two types of mutations

Somatic Mutation

• Mutations may occur in any cell and at any stage in the cell cycle.
• The immediate effect of the mutation and its ability to produce a phenotypic change are determined by its dominance, the type of the cell in which it occurs and when it happens relative to the life cycle of the organism.
• If the mutation occurs in a somatic cell, the mutant gene will be perpetuated only in somatic cells that descend from the original cell in which the mutation occurred.
• Examples: Delicious apple and the novel orange.
• Through vegetative propagation, they were later propagated as a mutant variety.

Germinal Mutation

• If dominant mutations occur in germ cells, their effects may be expressed immediately in progeny.
• If mutations are recessive, their effects are often obscured in diploids.
• If the mutation arises in a gamete, only a single member of the progeny is likely to have mutant gene.
• If mutations occur in germinal cells, several gametes may receive the mutant gene and thus enhance its potential for perpetuation.