Since the time DNA was discovered as the code of life, genetic analysis has greatly advanced our understanding of the relation between genotype and phenotype and associated molecular mechanisms in various organisms including plants and algae. Forward genetics from phenotype to genotype has identified causal genes of interesting phenotypes induced by chemical, ionizing-radiation, or DNA insertional mutagenesis. Meanwhile, reverse genetics from genotype to phenotype has revealed physiological and molecular roles of known gene sequences. During the past dozen years, many molecular genetic tools have been developed to investigate gene functions quickly and efficiently. In this chapter, we introduce several approaches of forward and reverse genetics, including random chemical and DNA insertional mutagenesis, activation tagging, RNA interference, and gene overexpression and induction systems, with some examples of genetic studies of chloroplast biology mainly in Arabidopsis thaliana. We also briefly describe methods for chemical and DNA insertion mutagenesis and how to obtain sequence-tagged mutants from public collections. With greatly improved DNA sequencing and genome-editing technologies, model organisms as well as diverse species can be used for molecular biology. Genetic analysis can play an increasingly important role in elucidating chloroplast biogenesis and functions.
Keywords: Arabidopsis; Chlorophyll; Chloroplast; Forward genetics; Mutant; Photosynthesis; Reverse genetics.