Transcription factors (AQA A-level Biology)

This fully-resourced lesson explains how the transcription of target genes can be stimulated or inhibited by transcription factors. Both the PowerPoint and the accompanying resources have been designed to cover the first part of point 8.2.2 of the AQA A-level Biology specification and links are continuously made throughout the lesson to the topic of protein synthesis which was covered in topic 4.2.

The lesson begins with a recall of the meaning of the terms genome and proteome so that a discussion can begin on whether a cell wants to express every gene and produce all of the possible proteins all of the time. As the answer to this is no, the idea of transcription factors is introduced. In order to fully understand this topic, students need to recall that the role of the promoter region is to bind RNA polymerase to initiate transcription. Students will learn that the factors have a DNA-binding domain and that some also have ligand-binding domains which allow molecules like hormones to bind. Moving forwards, the students are introduced to a group of substances called DELLA proteins which inhibit plant development. The way that transcription begins once the inhibition by the proteins has been removed is similar to the action of oestrogen and students are able to use this information as a guide during the final task where they have to order the sequence of events that take place once this steroid hormone binds to its transcription factor.