Nucleic acid: DNA

About this lesson

This unit focuses on DNA as the genetic material. It begins by presenting historical evidence that DNA, not protein, carries genetic information, including Griffith's bacterial transformation experiments, Avery's crucial enzyme experiment, and the Hershey-Chase bacteriophage experiment. It also discusses the evidence from comparing DNA quantities in somatic and reproductive cells. The unit then details the structure of the DNA molecule, including nucleotides, the sugar-phosphate backbone, base pairing rules (A=T, G=C), and the double helix model proposed by Watson and Crick, supported by Franklin's X-ray diffraction data. It explains DNA replication, covering the roles of enzymes like helicase, polymerase, primase, and ligase, and the concepts of leading and lagging strands and Okazaki fragments. The text also covers DNA repair mechanisms, the differences between prokaryotic and eukaryotic DNA (including plasmids), and how DNA is condensed in eukaryotic cells via histones and nucleosomes. Finally, it introduces the genome, repetitive DNA, and mutations, defining gene and chromosomal mutations, their origins (spontaneous and induced), and examples of desirable mutations.