For transcription to begin the gene needs to be stimulated by transciptional factors. These move from the cytoplasm into the nucleus. Each transcriptional factor has a site that binds to a specific region of DNA When it binds it stimulates transcription mRNA is then produced and translation into a polypeptide occurs. When the gene is not being expressed the site that the transcriptional factor binds to is blocked by an inhibitor molecule. The inhibitor molecule prevents the transcriptional factors from binding and thus prevents transcription One way which has been researched but you do not have to necessarily know about is the Lac Operon The example you have to know about is how the effect oestrogen has on transcription. Using figure 1 from page 214 and the information on page 240 produce a flow diagram of how oestrogen effect gene transcription. http://www.nature.com/focus/rnai/animations/inde x.html Watch the following animation and make notes, we are going to watch it twice so do not panic! Read through the two articles about how Andrew Z. Fire and Craig C. Mello were award the Nobel prize for their work in discovering si-RNA Task using you notes and the articles write a 5 minute speech explaining what si-RNA is, how it works and its significance to medicine. Complete the application questions from page 242 – 243 Start working on the exam style questions on page 244 – 245 these have to be completed for homework.