Which of the following is correct concerning fetal hemoglobin (HbF):

Appeared in: BHU NO-2019

Explanation

Fetal hemoglobin (HbF) is a tetrameric protein, which means it is made up of four globin chains.
The specific composition of HbF is two alpha (α) globin chains and two gamma (γ) globin chains.
This structure (α₂γ₂) is distinct from adult hemoglobin (HbA), which is composed of two alpha (α) and two beta (β) chains (α₂β₂).
The gamma chains are responsible for HbF's unique oxygen-binding properties, which are essential for fetal survival.

Option B: This statement is incorrect. Fetal hemoglobin (HbF) has a higher affinity for oxygen, not decreased. This property is vital for the fetus to efficiently extract oxygen from the maternal circulation across the placenta.
Option C: This describes the composition of adult hemoglobin (HbA), not fetal hemoglobin. HbA consists of two alpha (α) and two beta (β) subunits.
Option D: This is incorrect. While HbF is the predominant hemoglobin during fetal life, its production continues after birth. It gradually decreases and is replaced by adult hemoglobin (HbA) over the first 6 to 12 months of life. Small amounts can persist into adulthood, and levels can be elevated in certain medical conditions like sickle cell disease and thalassemia.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Properties and composition of Fetal Hemoglobin (HbF) as background academic context rather than a clinical decision trigger.
Understanding the high oxygen affinity of HbF is crucial for comprehending fetal physiology and how the fetus obtains oxygen in the relatively hypoxic uterine environment.
The switch from HbF to HbA production after birth is a key developmental milestone. Delays or failures in this switch are characteristic of certain hemoglobinopathies, such as beta-thalassemia.
In conditions like sickle cell disease, therapies aimed at increasing the levels of HbF in adults can be beneficial, as HbF interferes with the sickling process of red blood cells.

How to Approach the Question

First, identify the core subject of the question, which is 'fetal hemoglobin (HbF)'.
Recall the fundamental properties of HbF, including its structure, function (oxygen affinity), and the timeline of its presence.
Evaluate each option against these known facts.
Option A asks about the subunit composition. Recall that HbF is α₂γ₂.
Option B addresses oxygen capacity. Remember that HbF has a higher affinity for oxygen to draw it from the mother.
Option C presents another subunit composition. Recognize α₂β₂ as adult hemoglobin (HbA).

Concept Tested & Keywords

QAroVnyV3cV9G7Gdgf8hvr

E6 Nelson Textbook of Pediatrics(2024) — Volume 2 pp. 715-717, 716-718

E6 Obstetrics Williams p. 23-42

Practise the full BHU NO-2019

Attempt every question from this paper in a timed mock, then review the full solution for each one.