MCAT Biology Question — Fetal Hemoglobin | Next Step Test Prep MCAT Biology Question — Fetal Hemoglobin | Next Step Test Prep

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An individual is born with a mutation causing her to partially retain a form of fetal hemoglobin into adulthood. Compared to a normal individual, this person would exhibit:

 

A) no differences from a normal adult.
B) significantly reduced oxygen binding in the lungs.
C) no symptoms, since retention of fetal hemoglobin would be fatal.
D) increased oxygen binding to hemoglobin in the tissues.

 

Explanation

 

Fetal hemoglobin has a higher affinity for oxygen than does adult hemoglobin. Thus, it binds and holds oxygen more tightly. An individual with fetal hemoglobin would show increased oxygen binding to hemoglobin as a result. (A) is false because fetal and adult hemoglobin are different. (B) is false because fetal hemoglobin binds more to oxygen, not less. And (C) is false – in fact, reactivating fetal hemoglobin can be used as a treatment for sickle-cell. Therefore, the answer is (D).

 

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