Scientists have discovered that there are 20,000-25,000 protein-coding genes in the human genome. If a person has one allele for brown eye color and one for blue, the person's eyes will be brown.One gene pair dictates hair color.There have been genes found associated with a propensity to becoming overweight.0 most extreme places on Earth. The human genome has just over 3 billion DNA base pairs encoding 750 MB of information and containing 20,000-25,000 protein-coding genes.