Transformed host cells (AQA A-level Biology)

This detailed and engaging lesson looks at the culture of transformed host cells as an in vivo method to amplify DNA fragments. Both the PowerPoint and accompanying resources have been designed to cover the third part of point 8.4.1 of the AQA A-level Biology specification and ties in with the previous two lessons in this sub-topic on producing DNA fragments and the polymerase chain reaction.

The lesson begins with the introduction of the terms transgenic and transformed. Students will learn that bacterial cells are the most commonly transformed cells so the next task challenges their recall of the structures of these cells so that plasmid DNA can be examined from that point onwards. A quick quiz competition is used to introduce the key term, vector, and then the rest of the lesson looks at the details of the five steps involved in the transformation of the host cell:

• Remove and prepare the plasmid to act as a vector
• Insert the DNA fragment into the vector
• Transfer the recombinant plasmid into the host cell
• Identify the cells which have taken up the recombinant plasmid
• All the transformed host cells to replicate and express the novel gene

Time is taken to explore the finer details of each step such as the addition of the promoter and terminator regions, use of the same restriction enzyme to cut the plasmid as was used to cut the gene and the different types of marker genes. Links are continuously made to the previous lessons in this topic so that students feel confident to answer assessment questions which bring in knowledge from all of the sections.