GENE NUMBER, NOISE-REDUCTION AND BIOLOGICAL COMPLEXITY

Preliminary estimates suggest that gene number, and hence biological c omplexity, increased suddenly nt two periods of macroevolutionary chan ge (the origin of eukaryotes and the origin of vertebrates), but other wise remained relatively constant. As the genome is in constant flux, what normally constrains the number of different genes that an organis m can retain? Here, I suggest that an important limitation on gene num ber is the efficiency of mechanisms that reduce transcriptional backgr ound noise. The appearance of both eukaryotes and vertebrates coincide d with novel mechanisms of noise reduction.