Final answer:
The sickle cell mutation is a substitution mutation, specifically a point mutation in the hemoglobin gene, leading to the sickle-shaped red blood cells in sickle cell anemia. Therefore, the correct option is D.
Step-by-step explanation:
The sickle cell mutation is an example of a substitution mutation. This specific mutation occurs in the hemoglobin gene on chromosome 11, where a single nucleotide is replaced by another. More precisely, it is a point mutation where the amino acid glutamic acid is replaced by valine at the sixth position of the beta-globin chain due to a change from A to T in the DNA sequence. This single amino acid substitution significantly alters the properties of hemoglobin, which leads to the characteristic 'sickle' shape of the red blood cells associated with sickle cell anemia.