The sickle cells simply don't live as long as the normal cells, and so they eventually die at a quicker rate. And that leads to anemia, a lower blood count, a lower red blood cell count. Now, the question is, what exactly is the abnormality in the hemoglobin molecule? Well, it turns out it's a genetic abnormality. So instead of sequencing a specific polypeptide chain, we sequence a slightly different polypeptide chain. And in the case of sickle cell anemia, there's a single substitution of a single amino acid in the beta subunit of the hemoglobin molecule.