Population of the TATA⁺Inr⁺, TATA⁺Inr⁻, TATA⁻Inr⁺, and TATA⁻Inr⁻ potential promoter regions (PPRs) located in/outside of CpG islands. Solid bars represent population of PPRs located in CpG islands; shaded bars represent those outside of CpG islands in each category.