mendelian genetics, probability, pedigrees, and chi-square statistics introduction hemoglobin is a protein found in red blood cells (rbcs) that transports oxygen throughout the body. the hemoglobin protein consists of four polypeptide chains: two alpha chains and two beta chains. sickle cell disease (also called sickle cell anemia) is caused by a genetic mutation in the dna sequence that codes for the beta chain of the hemoglobin protein. the mutation causes an amino acid substitution, replacing glutamic acid with valine. due to this change in amino acid sequence, the hemoglobin tends to precipitate (or clump together) within the rbc after
