6.1.4 Gene Control: Transcription Factors

Question 1

How do transcription factors work?

Answer 1

• Bind to promoter region of gene
• Either allow or prevent transcription of gene
• Either increases or decreaess rate of transcription of a gene
• Eg. PIF is a transcription factor in plants activating transcription of amylase gene
• Allow RNA polymerase to bind to the transcription factor for transcription to occur

Question 2

Oestrogen and gene control

Answer 2

• Oestrogen (lipid soluble and can diffuse through plasma membrane)
• Moves into nucleus and binds to oestrogen receptors
• Change in shape of receptor is caused
• Receptor moves away from protein complex which it is usually attached to and binds to promoter region of its target gene
• So RNA polymerase binds to it and begins transcribing target gene

Question 3

Gibberellin and gene control

Answer 3

• Gibberellin is a hormone which controls seed germination by stimulating synthesis of amylase
• Influences transcription of amylase gene
• DELLA repressor protein bound to PIF, preventing PIF from binding to promoter of amylase gene so no transcription of amylase occurs
• Gibberellin binds to a gibberellin receptor and enzyme, which stimulates the breakdown of DELLA
• PIF detaches from DELLA
• PIF can bind to amylase gene, transcription of amylase gene begins
• Amylase produced