QUESTION 4 (3 marks)
Explain how transcription factors allow for cell differentiation, using an example.
QCAA guide · typeset solution
QCAA sample response and mark allocation
4 | Transcription factors are proteins that turn specific genes on or off by binding to nearby sections of DNA. This allows different genes to be expressed in different cell types. For example, the SRY gene on the Y chromosome promotes the development of testes by producing a protein that regulates the expression of genes (production of proteins) required by Sertoli cells. | • recognises that transcription factors bind to specific DNA sequences [1 mark] • explains that this allows different genes to be expressed in different cell types [1 mark] • provides an example [1 mark] |
QCAA sample response and marking criteria reproduced from the official guide.
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