Gene number

The number of genes each organism contains has turned out to be much lower than expected. Also, the number of genes in an organism is not well correlated with the organism's complexity (Claverie, 2001). For example, the human genome is estimated to consist of around 35,000 genes - less than that in rice. How can this be?

Approximate gene numbers:
 

Organism Yeast C. elegans (worm) Fruit fly Arabidopsis Human

Number of genes 6,000 19,000 13,000 -14,000 25,000 30,000 - 40,000