Lesson 22 – DNA and RNA
In this lesson, students focus on how nucleotides polymerize into DNA and RNA. While many people are familiar with genes as things that “make us who we are,” the past 20 lessons give students the proper atomic-level resolution on which to truly understand genetics. The lesson also introduces the often-neglected structures of transfer RNAs and ribosomes. Ribosomes are RNA-based enzymes that catalyze the synthesis of proteins. That RNAs are required to make proteins provides strong evidence that RNA pre-dates proteins, and that an “RNA-world” existed before DNA and protein dominated biochemistry. The lesson draws on crystal structures of ribosomes, only recently published, which provide an unprecedented glimpse into these living molecular fossils, relics from biology’s deep past.