Why are patents on seeds dangerous?

"Monopoly control of crop genes is a bad idea under any circumstances. But in the midst of a global food crisis with climate change looming, such control is unacceptable and must be challenged. Patented gene technologies will concentrate corporate power, drive up costs, inhibit independent research, and further undermine the rights of farmers to save and exchange seeds. Globally, the top 10 seed corporations already control 57% of commercial seed sales. A handful of transnational seed and agrochemical companies are positioned to determine who gets access to patented genes and what price they must pay." (Thanks Steve)