Genotype is the genetic constitution of an individual organism, it indicates the certain gene that an individual is carrying. Genotype is part of the genetic makeup of a cell. The red blood cells contains hemoglobin : Hemoglobin is a substance which helps in carrying oxygen to the tissues. Hemoglobin comprise of - Heme and Globin; the heme and globin are two pairs of protein chain. When we have an amino acid substitution, specifically in the globin chain, then certainly, there is an abnormality. Note : Amino acid are the building blocks of protein. Let's say the chain suppose to consist of amino acid 'D' but it is instead substituted for 'F' at a particular point of the chain, then, there is definitely an error which would lead to abnormality. Types of genotype - AA : At the sixth position of both Globin chains, we have 'Glutamate'(Normal) - AC : At the sixth position of one of the Globin chains, we have 'Lysine