Regulation of transcription and translationAQA A-Level Biology: Flashcards

Exam questions on Regulation of transcription and translation

1. Oestrogen is a steroid hormone released by the ovaries. In a target cell of the uterus lining, oestrogen enters the cytoplasm and binds to a specific receptor protein. The oestrogen-receptor complex then moves into the nucleus. Cells that lack this receptor protein, such as most muscle cells, do not respond to oestrogen.
   Explain why oestrogen changes gene expression in cells of the uterus lining but not in most muscle cells.2 marks
2. Researchers followed a pair of identical twins from childhood to the age of 50. Both twins have the same DNA base sequence. At the age of 3 the pattern of DNA methylation in their cells was almost identical. At 50 one twin, who smoked and had a very different diet, had much more methylation of the promoter region of one gene, and cells from this twin contained far less mRNA from that gene.
   Explain how the two twins can show different gene expression even though their DNA base sequences are identical.2 marks
3. Researchers are developing a treatment for a disorder in which liver cells translate too much of a harmful protein. They design short double-stranded RNA molecules, with a base sequence matching part of the mRNA for the protein, and add them to cultured human liver cells. The protein production fell by 85%, but the amount of DNA and the rate of transcription of the gene did not change.
   Describe how RNA interference (RNAi) can inhibit translation of the mRNA for the harmful protein.3 marks