Microarrays (Edexcel Int. A-level biology)

This lesson explains how labelled DNA probes in microarrays can be used to identify active genes. The PowerPoint and accompanying resources have been designed to cover the content of point 8.20 of the Edexcel International A-level biology specification.

The lesson begins by introducing the BRCA genes, and the students will learn how faulty alleles of these two genes can increase an individual’s risk of developing breast cancer. Therefore, there is a need to be able to locate specific alleles like these, and this function is performed by DNA probes. The students are challenged to use the function of the probes to predict their structure and will understand that they are short lengths of single stranded DNA that have a base sequence complementary to the base sequence of part of the target allele. A quick quiz round is used to introduce hybridisation as a key term, to ensure that students recognise that the probe will bind if the complementary base sequence is encountered. Moving forwards, a DNA microarray is introduced to show that it’s possible to screen for multiple genes.

The remainder of the lesson considers how the DNA probes are used to screen for heritable conditions and drug responses, and real-life examples are used to increase relevance.