Between a chicken and a grape: estimating the number of human genes

Abstract

Many people expected the question 'How many genes in the human genome?' to be resolved with the publication of the genome sequence in 2001, but estimates continue to fluctuate.

Figure 1

Gene counts in a variety of species. Viruses, the simplest living entities, have only a handful of genes but are exquisitely well adapted to their environments. Bacteria such as Escherichia coli have a few thousand genes, and multicellular plants and animals have two to ten times more. Beyond these simple divisions, the number of genes in a species bears little relation to its size or to intuitive measures of complexity. The chicken and grape gene counts shown here are based on draft genomes [50,51] and may be revised substantially in the future.

Figure 2

The trend of human gene number counts together with human genome-related milestones. Individual estimates of the human gene count are shown as blue diamonds. The range of estimates at different times is shown by the two vertical blue dotted lines. Note how this range has narrowed in recent years.