20.3: Regulation of transcription and translation

Question 1

How is transcription controlled

Answer 1

For transcription to be begin, the gene is switched on by transcriptional factors.

Transcriptional factors contain a site that binds to a specific base sequence of DNA in the nucleus

Once transcriptional factors bind, it causes the DNA to undergo transcription

mRNA is produced and the information it carries is translated into a polypeptide

When a gene is not expressed, the site on the transcriptional factor is said to be ‘not-active’

Inactive transcriptional factor = no transcription

Question 2

Role of oestrogen in the regulation of transcription

Answer 2

1. Oestrogen is lipid-soluble so it can freely move through the phospholipid portion of the membrane
2. Once inside the cytoplasm, it binds with a site on a receptor molecule of the transcriptional factor. The shape of the site and the shape of oestrogen compliment one another
3. By binding with the site, the oestrogen changes the shape of the DNA binding site on the transcriptional factors, which can now bind to DNA
4. The transcriptional factor can now enter the nucleus through a nuclear pore and bind to specific base sequences on DNA
5. The combination of the transcriptional factor with DNA stimulates transcription of the gene that makes up the portion of DNA

Question 3

What is the role of oestrogen

Answer 3

Binds with a site on a receptor of a transcription factor and causes the DNA binding site to change shape.

Question 4

What receptors does oestrogen work on

Answer 4

Only target cells have the oestrogen receptor so only these cells respond to the stimulus of oestrogen

Question 5

What is the role of a transcriptional factor

Answer 5

Transcriptional factors bind to a specific DNA base sequence and cause transcription to begin.

Each transcription factor has a site that binds to a specific base sequence