8.2.5

Regulating Transcription

Test yourself on Regulating Transcription

Test your knowledge with free interactive questions on Seneca — used by over 10 million students.

Transcription Factors

Genes are expressed by transcription and translation. In eukaryotic cells, not all of the genes are expressed in a specialised cell. Gene expression is controlled by transcription factors.

Function

Function

  • Transcription factors are proteins that control gene expression by stimulating or inhibiting the transcription of target genes.
  • Transcription factors are produced in the cytoplasm and move to the nucleus.
  • In the nucleus, transcription factors bind to a specific region of DNA to stimulate or inhibit the gene.
Activators

Activators

  • Transcription factors that stimulate gene expression are called activators.
  • Activators promote the transcription of the genes by interacting with an enzyme called RNA polymerase and allowing it to bind to DNA.
Repressors

Repressors

  • Transcription factors that inhibit gene expression are called repressors.
  • Repressors prevent the transcription of genes by stopping RNA polymerase from binding to DNA.

Hormones

Transcription can also be regulated by hormones. There are two types of hormone involved:

Peptide hormones

Peptide hormones

  • Peptide hormones bind to the cell surface membrane and trigger a secondary messenger response.
  • The secondary messenger will lead to the activation or inhibition of transcription of some genes.
Lipid-soluble steroid hormones

Lipid-soluble steroid hormones

  • Lipid-soluble steroid hormones can pass through the phospholipid membrane.
  • Steroid hormones interact directly with DNA to promote or inhibit gene expression.
    • E.g. Oestrogen.

Oestrogen

Oestrogen is a lipid-soluble steroid hormone that can enter the cell and directly interact with DNA to initiate gene transcription. The steps involved are:

1) Enter the cell

1) Enter the cell

  • Oestrogen enters the cytoplasm of the cell through the cell surface membrane.
  • Oestrogen is lipid-soluble so it can pass through the phospholipid bilayer.
2) Bind to transcription factors

2) Bind to transcription factors

  • Oestrogen binds to receptors on transcription factors in the cytoplasm.
  • Binding of oestrogen causes the transcription factors to change shape.
  • The transcription factors form a receptor-hormone complex that can now enter the nucleus.
3) Bind to DNA

3) Bind to DNA

  • The receptor-hormone complex binds to the promoter region of the DNA.
  • Binding to DNA activates transcription.
  • This stimulates protein synthesis.
Jump to other topics
1

Biological Molecules

2

Cells

3

Substance Exchange

4

Genetic Information & Variation

5

Energy Transfers (A2 only)

6

Responding to Change (A2 only)

7

Genetics & Ecosystems (A2 only)

8

The Control of Gene Expression (A2 only)

9

Mathematical Skills

Practice questions on Regulating Transcription

Can you answer these? Test yourself with free interactive practice on Seneca — used by over 10 million students.

  1. 1
  2. 2
  3. 3
  4. 4
  5. 5
Answer all questions on Regulating Transcription

Unlock your full potential with Seneca Premium

  • Unlimited access to 10,000+ open-ended exam questions

  • Mini-mock exams based on your study history

  • Unlock 800+ premium courses & e-books

Get started with Seneca Premium