Several characteristic features of the structural organization of chlo
roplast and mitochondrial genomes of higher plants are compared. The f
actors that determine the size of chloroplast and mitochondrial genome
s (the presence of repeated sequences, promiscuous DNA, gene content,
and the occurrence of introns) are discussed. The mode of genome evolu
tion in chloroplasts and mitochondria are reviewed. In a separate chap
ter, the available data on the structural organization of algal genome
s are presented.