Biology 1002B Lecture Notes - Lecture 19: Hemoglobin, Thymine, Prokaryote

• School: Western University
• Department: Biology
• Course: Biology 1002B
• Professor: Tom Haffie

Document Summary

Mechanisms for his- reversion to his+ in ames test: Lecturer tom haffie used the ames test to find mutagens in wine. The system of study was based on salmonella bacteria, which already had mutants that could not make their own histidine (his-). In a minimal medium (lacking in histidine) these mutant cells cannot survive. Throughout the duration of the ames test, some of the mutant cells revert back to the normal his+ genotype. This reversion from mutant to normal genotype is still a mutation. Such reversion is upon which the ames test is based since in a minimal medium, spontaneous revertants are only present in the wild type. Small amounts of histidine are essential in the medium in order to allow the mutants to divide, but about 30 of them are able to actually grow and survive. For most mutation to occur, replication is required.