20.3 Regulation of transcription and translation

Question 1

What are transcriptional factors

Answer 1

• These control which genes are expressed, as they can turn on the gene that needs to be transcribed

They come from the cytoplasm

Question 2

How do transcriptional factors work

Answer 2

-These turn on the gene that needs to be transcribed, and they move from cytoplasm into the nucleus

• Each transcriptional factor has a site that binds to specific base sequence on DNA in nucleus
• When it binds, it causes that region of DNA to begin transcription
• mRNA is then produced and the information it carries is translated into a polypeptide

Question 3

How do transcriptional factors stop genes being expressed

Answer 3

When a gene is not being expressed (is switched off), the site on the transcriptional factor that binds to DNA is not active

So as the site isn’t active, there will be no transcription or translation

Question 4

How does oestrogen switch on a gene and start transcription

Answer 4

• Oestrogen can bind with receptor site on transcriptional factor
• This activates DNA binding site by causing it to change shape

Question 5

What is the process of oestrogen switching on a gene

Answer 5

• Oestrogen is lipid soluble so diffuses through phospholipid bilayer of cell membrane
• Once in cytoplasm, oestrogen binds to site on transcriptional factor as they’re complimentary
• By binding to the site, the DNA binding site on transcriptional factor changes shape and can now bind to DNA (so is active)
• The transcriptional factor can now enter the nucleus through a nuclear pore and bind to specific base sequence on DNA.
• This stimulates transcription of that gene