During embryonic development, which globin chain functionally replaces the adult β chain in embryonic hemoglobins?

Introduction:
Hemoglobin expression is developmentally regulated. Distinct globin chains are expressed in embryonic, fetal, and adult stages to optimize oxygen delivery across changing physiological conditions.

Given Data / Assumptions:

• Embryonic hemoglobins (e.g., Hb Gower-1, Hb Gower-2) are under consideration, not fetal HbF or adult HbA.
• Adult β chains are minimal or absent during early embryogenesis.

Concept / Approach:

Embryonic hemoglobins pair ζ (zeta, α-like) with ε (epsilon, β-like) chains. Later, fetal hemoglobin uses γ (gamma) instead of β; finally, adult hemoglobin uses β with α.

Step-by-Step Solution:

Verification / Alternative check:

Globin gene clusters show temporal switches: ε (embryo) → γ (fetus) → β (adult).

Why Other Options Are Wrong:

γ is fetal, not embryonic; δ is a minor adult chain; α is present but does not replace β in the β-like role; ζ is α-like, not β-like.

Common Pitfalls:

Confusing fetal (γ) with embryonic (ε) hemoglobins.

Final Answer:

Epsilon (ε)