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• Incomplete dominance: The inheritance of flower colour in Antirrhinum (Snapdragon), where a cross between red and white flowers produces pink flowers, is a classic example .
• Co-dominance: ABO blood grouping in humans is a good example where both alleles ( and ) express themselves equally .
• Pleiotropy: Phenylketonuria is an example where a single gene mutation exhibits multiple phenotypic expressions (mental retardation, reduction in hair/skin pigmentation) .
• Polygenic inheritance: Human skin colour is controlled by three or more genes, making it a classic example of polygenic inheritance .