Gel electrophoresis (CIE International A-level Biology)

This fully-resourced lesson explains how gel electrophoresis is used to analyse nucleic acids and proteins and explores its applications in forensic science and medical diagnosis. The engaging and detailed PowerPoint and accompanying resource have been written to cover point 19.1 (d) of the CIE International A-level Biology specification

As a whole lesson, each step of the genetic fingerprinting process is covered but with the main focus on gel electrophoresis within this process. Students will be introduced to STRs and will come to recognise their usefulness in human identification as a result of the variability between individuals. Moving forwards, the involvement of the PCR and restriction enzymes are discussed and students are challenged on their knowledge of this process and these substances as they were encountered in a previous lesson. The main section of the lesson focuses on the use of gel electrophoresis to separate DNA fragments (as well as proteins) and the key ideas of separation due to differences in base pair length or molecular mass are discussed and explained. As well as current understanding checks, an application question involving Huntington’s disease is used to challenge their ability to apply their knowledge of the process to an unfamiliar situation. The remainder of the lesson describes how the DNA is transferred to a membrane and hybridisation probes are used to create a pattern on the X-ray film.

Time has been taken to make continuous links to the previous lessons in topic 19.1 as well as those from topic 6 where DNA, RNA and protein synthesis were introduced.