Actinomycin D is a chemotherapy drug and polypeptide antibiotic isolated from soil bacteria of the genus Streptomyces. It functions as a selective inhibitor of transcription by binding to DNA at the transcription initiation complex, preventing the elongation of the RNA chain by RNA polymerase. It has no direct inhibitory effect on the translation machinery or ribosomes.
Describe the process of protein synthesis in a eukaryotic cell, starting from a gene in the nucleus.
Explain why cellular protein synthesis does not halt immediately upon exposure to actinomycin D, but does gradually cease entirely over a longer period.
Explain how the molecular structure of a gene determines the specific primary structure of the protein produced.
72 exam-style questions on OCR GCSE Biology 1.2 What happens in cells (and what do cells need)?, covering 1.2.1 Structure of DNA, 1.2.2 Nucleotides and complementary bases, 1.2.3 Protein synthesis, 1.2.4 DNA structure and the proteins made, 1.2.5 Investigating enzymatic reactions, and 1.2.6 Mechanism of enzyme action. Each one has a worked solution and a mark scheme showing where the marks go.