The delay of the expression of a newly acquired character. Mutations may appear in a bacterial population several generations after the administration of a mutagen. Phenotypic lag may be due to any of the following reasons: (1) The mutagen may inactivate the gene at once, but this inactivity may not become apparent until the products previously made by the gene are diluted to a sufficient degree. A number of cell divisions occur before the concentration of these products falls below some critical level. (2) The “mutagen” may itself be inactive. It may undergo a series of reactions to yield a compound that is the true mutagen. The latent period would then be the time required for those reactions to take place. (3) The mutagen may cause the gene to become unstable. At a later time, it will return to a stable wild type or mutant state. (4) The microbe may be multinucleate, and a mutation may occur in but one nucleus. The latent period then would be the time required for nuclear segregation. See perdurance.
Subjects: Genetics and Genomics.