Summary Notes on gene control in eukaryotes.

Gene control in eukaryotes

Some genes are transcribed all the time to produce constituitive proteins;
others are only 'switched on' when their protein products are required.




Transcription factors bind to the promoter region of a gene. This may increase
or decrease the transcription of the gene. Their roles are to make sure that
genes are expressed in the correct cell at the correct time and to the
correct extent.

Effects of transcription factors:


• form part of the protein complex that binds to the promoter region of the
gene
• activate appropriate genes in sequence
• determination of sex in animals
• allow responses to environmental stimuli
• regulate cell cycle, growth and apoptosis
• give hormones their effect


Gibberellin (a plant hormone) controls seed germination in plants
such as wheat and barley by stimulating the synthesis of amylase.

- DELLA protein inhibits the binding of a transcription factor to the gene
promoter PIF
- gibberellin causes the breakdown of DELLA protein
- gibberellin allows PIF to bind to its target promoter
- transcription of the gene can take place