Gene control by transcription factorsEdexcel A-Level Biology A: Flashcards

What these 12 flashcards ask

What is gene expression?
Why do a liver cell and a muscle cell make different proteins?
What is a transcription factor?
What is the promoter?
How does an activator transcription factor work?
How does a repressor switch a gene off?
Why does each transcription factor affect only certain genes?
Why can steroid hormones enter cells directly?
What does oestrogen bind to inside a target cell?
How does the oestrogen-receptor complex alter gene expression?
Why does a hormone affect only target cells?
Why is it useful for cells not to express all their genes?

Exam questions on Gene control by transcription factors

A researcher compares a liver cell and a skeletal muscle cell taken from the same person. Both cells contain exactly the same genome, but the two cells make very different sets of proteins.
Explain how a transcription factor can switch on a gene.2 marks
Oestrogen is a steroid hormone that stimulates cells lining the uterus to make particular proteins. Oestrogen is lipid-soluble and acts by entering its target cells.
Explain why oestrogen affects only certain cells in the body.2 marks
A scientist grows human cells in culture and measures the amount of mRNA made from gene X, in arbitrary units, after 6 hours. Cells with no oestrogen contained 4 units. Cells given oestrogen contained 52 units. Cells given oestrogen together with a drug that blocks the oestrogen receptor contained 5 units.
Calculate the percentage increase in mRNA from gene X caused by oestrogen alone.3 marks

Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).