6.1.4 Gene Control: Transcription Factors

Question 1

What do eukaryotes use to control gene expression?

Answer 1

Transcription factors

Question 2

What are transcription factors?

Answer 2

Proteins that bind to specific regions of DNA to control the transcription of DNA to control the transcription of genes

Question 3

What percentage of human genes code for transcription factors?

Answer 3

~10%

Question 4

What do transcription factors allow organisms to do?

Answer 4

To respond to their environment
Some hormones achieve their effect via transcription factors

Question 5

What does the presence of a transcription factor do?

Answer 5

Either increase or decrease the rate of transcription of a gene

Question 6

Give an example of gene control using oestrogen

Answer 6

Oestrogen diffuses through plasma membrane and into nucleus
Oestrogen attaches to receptor (that is contained within protein complex)
Oestrogen receptor changes shape and leaves protein complex
Oestrogen receptor can now attach to promoter region of target gene
Oestrogen receptor attracts other cofactors to bind with it, enabling RNA polymerase to transcribe the target gene

Question 7

What is necessary for the synthesis of amylase?

Answer 7

The breakdown of DELLA protein by gibberellin

Question 8

What is gibberellin?

Answer 8

A plant hormone that controls seed germination by stimulating the synthesis of the enzyme amylase

Question 9

What happens when gibberellin is applied to a germinating seed

Answer 9

There is an increased amount of the mRNA for amylase present

Question 10

What components are involved in the breakdown of DELLA protein by gibberellin?

Answer 10

• Repressor protein DELLA
• Transcription factor (PIF)
• Promoter of amylase gene
• Amylase gene
• Gibberellin
• Gibberellin receptor and enzyme

Question 11

Describe the process of the breakdown of the DELLA protein by gibberellin

Answer 11

PIF (transcription factor) is bound to della and unable to bind to promoter
Gibberellin binds to gibberellin receptor and enzyme which starts the breakdown of DELLA
Tanscription factor is no longer bound to DELLA protein and so it binds to promoter of amylase gene
Transcription of amylase gene begins
Amylase is produced

Question 12

Why is RNA analysis important with regards to gene expression?

Answer 12

When a cell expresses a gene, RNA is produced by transcription. This RNA present can be analysed and scientists can match it to specific genes and work out which genes are being expressed in that specific cell