Several amino acid substitutions in the α and β chains of human hemoglobin are shown in the following table. Hb Type Normal Amino Acid Substituted Amino Acid Hb Toronto Ala Asp (α-5) HbJ Oxford Gly Asp (α-15) Hb Mexico Gln Glu (α-54) Hb Bethesda Tyr His (β-145) Hb Sydney Val Ala (β-67) HbM Saskatoon His Tyr (β-63) Using the code table (Figure 13.7), determine how many of them can occur as a result of a single-nucleotide change.