The proteins that we eat are digested into amino acids that circulate to the cells where the translation process takes place according to our genetic program.
The proteins then formed due to the translation process have a new, different, amino acid sequence and number, and they also determine our phenotype. Red Blood Cells (RBC's): Are a-nucleated cells, they have biconcave disc-shape and contain complex proteins called hemoglobin. Hemoglobin (Hb): Carries respiratory gases (carbon dioxide and oxygen). Hemoglobin + Oxygen <------> Oxyhemoglobin (HbO2) Hemoglobin + Carbon dioxide <------> Carboxyhemoglobin (HbCO2) Hemoglobin in healthy RBC's is called HbA, however, in sickle blood cells it's called HbS.
People having HbS will have abnormal RBC's that are not able to carry respiratory gases, and that's how protein-synthesis effects the phenotype of an individual.
A mutation in the amino acid sequence causes the blood abnormalities.