BIOLOGY 151 Lecture Notes - Lac Repressor, Model Organism, Galactose

• School: UMASS-Amherst
• Department: Biology
• Course: BIOLOGY 151
• Professor: Mark Huyler

Document Summary

In bacteria, gene expression can be controlled at three levels: transcription, translation or post-translation (protein activation) Changes in gene expression allow bacterial cells to respond to environmental changes. Transcriptional control can be negative or positive. Negative control occurs when a regulatory protein prevents transcription. Positive control occurs when a regulatory protein increases the transcription rate. A cell does not express all of its genes at the same time. Instead, the are very selective about the genes. Eschericha coli has served as an excellent model organism for the study of prokaryotic gene regulation. Like most bacteria, e. coli can use a wide array of carbohydrates to supply carbon and energy. Control of gene expression allows e. coli to respond to its environment and switch its uses of sugars. Gene expression in bacteria was predicted to be triggered by specific signals from the environment. Translational control allows the cell to prevent the translation of an mrna molecule that has already been transcribed.