Humans have around 100,000 genes
The core idea stands, but key numbers or details have changed.
TaughtThe human genome contains roughly 100,000 genes: we are complicated animals, so we must need a lot of them.
NowAbout 19,000 to 20,000 protein-coding genes. The Human Genome Project's draft in 2001 and completion in 2003 cut the estimate by a factor of five.
What actually happened
The 100,000 figure came from a back-of-the-envelope calculation in the 1960s and stuck around because it felt right. Human beings are elaborate; surely we need more genes than simpler creatures. Scientists ran an actual betting pool on the number as sequencing approached, and almost everyone bet too high.
The answer humbled us: roughly the same count as a nematode worm, and fewer than a grape or a rice plant. Complexity does not come from gene count. It comes from regulation, alternative splicing that lets one gene produce many proteins, and the timing of when genes switch on. Note the change type here: this is an updated number, not a disproved concept. Genes exist, DNA carries them, and the central idea your biology class taught is intact. Only the arithmetic moved.
Newsletter
Get new weekly revisions
Sources
Who was taught this
Still standard through 2004, so anyone who finished school between 1950 and 2003 learned the earlier version.