Which subtype of hemoglobin is not considered a normal embryonic form?

The correct answer is that Hb A is not considered a normal embryonic form of hemoglobin. Hemoglobin A is the most common type of hemoglobin found in adult humans, comprising about 97% of the total hemoglobin in adults. It is primarily responsible for transporting oxygen and is formed after the embryonic and fetal stages of development.

On the other hand, Gower 1, Gower 2, and Portland hemoglobin are all types of embryonic hemoglobins produced during the early stages of fetal development. Gower 1 consists of two epsilon and two zeta chains, while Gower 2 contains two alpha and two epsilon chains. Portland hemoglobin is made up of two zeta and two gamma chains. These forms of hemoglobin are crucial for the developing embryo and fetus, as they possess a higher affinity for oxygen, allowing effective oxygen transport in the low-oxygen environment of the womb.

This distinction emphasizes the developmental progression from embryonic to adult hemoglobins, highlighting that Hb A is not a form found during embryonic development.