Variation in gene numbers among eukaryotes

Gene numbers in various organisms remind us that evolution is not necessarily progressive. Single-celled yeasts have smaller numbers of genes than do multi-cellular organisms, but invertebrates such as flies and worms do not vary greatly from humans. The higher number of genes in flowering angiosperms reflect additional metabolic functions (including photosynthesis) with respect to animals. The exceptionally high number in maize is likely due to its origin as a cultivated polyploid species that has become partially diploidized through divergence of duplicated gene loci. Compare this table with the chart of C-value [total DNA content].

Figure ©2012 TA Brown, Introduction to Genetics (1st ed.); additional text ©2016 by Steven M. Carr