HbC

mutation of 6th aa of betaglobin protein

Glu-->Lys

crystalloids form, reducing survival time of RBC

HbS in hypoxic environment

precipitate as tactoids or long arrays, polymers of deoxy Hb (T state)

sickling

balanced polymorphism

when heterozygous genotype confers survival advantage

ex: sickle cell trait (AS) --> malaria resistance

Solubility test

blood + ionic solution

HbS has low solubility in this solution-->opaque

CANNOT DISTINGUISH TRAIT FROM DISEASE

Hb electrophoresis

HbS test

migration of proteins

quantitation (scan)

after electrophoresis, gel can be scanned to measure relative mixture of Hb types

RFLP and sickle cell

SS would show up as 1 band, not 2 because mutation would prevent cleavage by MstII

populations most affected by sickle cell disease

#1: African Americans

#2: Native Americans

in the world, prevalence in Africa and India and some Middle East

SCD Tx

partial-exchange transfusion (risk of iron overload--transfusion-induced hemosiderosis)

bone marrow transplantation

induction of HbF synth (hydroxyurea)