DNA and GENES (AQA A-level Biology)

This fully-resourced lesson looks at the structure of genes and explores their role as a base sequence on DNA that codes for the amino acid sequence of a polypeptide. Both the PowerPoint and accompanying resource have been designed to cover the second part of point 4.1 of the AQA A-level Biology specification and has been written to specifically tie in with the previous lesson on DNA in prokaryotes and eukaryotes.

The lesson begins with a prior knowledge check as the students have to recognise the key term chromosome from a description involving DNA and histones. This allows genes, as sections of a chromosome, to be introduced and the first of a number of quiz rounds is then used to get the students to meet the term locus so that they can understand how each gene has a specific location on a chromosome. Whenever possible, opportunities are taken to make links to the other parts of the AQA specification and this is utilised here as students are reminded that alternative versions of a gene (alleles) can be found at the locus. Moving forwards, students will learn that 3 DNA bases is a triplet and that each triplet codes for a specific amino acid. At this point, the genetic code is introduced and students are challenged to explain how the code contains 64 different triplets. By comparing this number against the number of different amino acids in proteins, students will see how each amino acid is encoded for by more than one triplet and how this explains the degenerate nature of the genetic code. Again, an opportunity is taken to link to gene mutations. Finally, the students are told that most of the nuclear DNA in a eukaryote doesn’t code for a polypetptide and that even within a gene, there are coding and non-coding regions known as exons and introns respectively. The last section of the lesson uses a quiz round to check on all of the key terms which have been met in the two lessons on DNA, genes and chromosomes.