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Haemoglobin
Mutations (Foetal Haemoglobin
(HbF) (contains two γ-chains…
Haemoglobin
Mutations
Foetal Haemoglobin
(HbF)
-
mutation enables preferential binding of oxygen, allowing the fetus to pull O₂ from maternal blood.
-
Sickle Cell
(HbS)
a single amino acid mutation ─ a polar glutamic acid (Gla6) is replaced by a nonpolar lysine residue.
enables abnormal hydrophobic interactions between haemoglobin molecules, causing polymerisation.
when in the deoxygenated form, aggregates to form linear polymers that distort red blood cells
the "sickle-shaped" red blood cells get stuck in capillaries, causing a range of debilitating secondary effects.
Methaemoglobin
(MetHb)
refer to mutations that arise from the oxidation of the haem iron to Fe³, which O₂ cannot interact with.
-
Hb-Christchurch
caused by a single amino acid mutation ─ large, nonpolar Phe is replaced by a small, polar Ser.
as a consequence of the mutation, the haem group is slightly destabilised ─ effects are not as serious as in other mutations.