Non Mendelian

• Incomplete Dominance - the phenotype of F1 hybrids is somewhere between the phenotypes of the two parental varieties

  
• Codominance - two dominant alleles affect the phenotype in separate, distinguishable ways

  
• Multiple alleles

  • Most genes exist in populations in more than two allelic forms
  • For example, the four phenotypes of the ABO blood group in humans are determined by three alleles for the enzyme that attaches A or B carbohydrates to red blood cells: I A , I B, and i
  • The enzyme encoded by the I A allele adds the A carbohydrate, whereas the enzyme encoded by the I B allele adds the B carbohydrate; the enzyme encoded by the i allele adds neither

  
• Epistasis - is a genetic phenomenon where the expression of one gene affects or masks the expression of another gene. It refers to the interaction between two or more genes to determine the phenotype (observable characteristics) of an organism.

  
• Polygenic inheritance - refers to the inheritance pattern of traits that are controlled by multiple genes, each with a small additive effect on the phenotype. Often display a wide range of phenotypic variations in a population often called Quantitative characters.

  eg. Height and Skin Color