Final answer:
The shape that Hgb S causes RBC's to form is crescent or sickle-shaped, a condition associated with the genetic disorder sickle cell anemia. These sickle-shaped red blood cells can lead to various health problems due to their tendency to obstruct capillaries.
Step-by-step explanation:
The shape that Hgb S makes the RBC's is crescent or sickle-shaped. This abnormal shaping occurs due to a genetic disorder known as sickle cell anemia, which produces an abnormal type of hemoglobin called hemoglobin S. Under low oxygen concentrations, this abnormal hemoglobin causes the erythrocytes, or red blood cells, to deform and assume a sickle shape. These sickle-shaped red blood cells are less efficient in carrying oxygen and can get trapped in narrow blood vessels, leading to a variety of health complications.
Normally, erythrocytes are disc-shaped with a biconcave form that optimizes the surface area to volume ratio. This characteristic shape is beneficial for gas exchange and allows the cells to fold and maneuver through capillaries easily. However, the precipitation of Hgb S within the red blood cells during sickle cell anemia disrupts this natural shape, causing significant health effects.