Characteristics of Hemoglobin variants and Hb
Different Hemoglobin combinations
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Hemoglobin VariantsHemoglobin Variants
? There must be 2 Alpha and 2 non alpha for oxygen carrying
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function, which differs at different stages of foetal and early
neonatal life
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? Normal adult hemoglobin (HbA) consists of four polypeptidechains 22
? Normally in adult blood, small quantities of two other varieties of
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hemoglobins i.e. HbA2 and HbF are found.
Normal Hemoglobin Variants
Type
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Embryonic
Hb
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Fetal HbAdult Hb
Hb Gower-1
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Hb F
Hb A
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Hb A2structure
22
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22
22
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22Primary Hb in
Normal %
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embryonic
0.5-0.8 %
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96-98 %2.0-3.0 %
life 8 wks
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Normal Hemoglobin Variants
HbA (22)
96% to 98 %
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This is basic form of Hb which is important in transport of gases O2 and CO2.HbA2 (22)
After 6 months to 1 year = 02% to 03 %
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Normal Hemoglobin VariantsFetal hemoglobin (22)
- 141 amino acids
Lifespan of RBC containing HBF is decreased to 80 days only
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Embryonic Hb
Hb Gower-1 (22) Primary Hb in embryonic life 8 wks
Portland-1 (22) is the -substituted counterpart of fetal HbF (22) (By 12 weeks of
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gestation, embryonic Hb changes into HbF.Hb Portland-2 (22) since it occurs only in cases of an extreme type of -thalassemia.
Importance of Fetal hemoglobin (22) in fetal life
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HbF can take up large volume of oxygen atlower PO2.
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Abnormal hemoglobin Variants - HemoglobinopathiesGLOBIN CHAINS
The genes for the synthesis of globin are present on chromosome 16 () and
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chromosome 11 ().This determines the different variants of hemoglobin (Normal and abnormal) present at
different ages.
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Globin genes and hemoglobin molecules
Sickle Cell Disease (HbS)
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First molecular disease to be recognized.
chains are normal and basic abnormality is in beta chain due to a point
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mutation.SICKLE CELL DISEASE
SICKLE CELL TRAIT
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Homozygous -HBSS
Heterozygous - HbAS
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Sickle Cell Disease? Most common Hb variant
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Sickle Cell DiseaseHb S molecules are only 20% as soluble as Hb
A in deoxygenated blood,
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low oxygen tension, Hb S molecules
polymerize
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causing sickle shaped RBCsSelf Assessment
Jaundice is also called as ------------------------------when serum bilirubin is above ---------------------
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The baby at birth has ------------------------------------------------------------ and excessive RBCs destruction80% of ------------------------------- is excreted in feces as ---------------------------, which gives brown color of stool and
20% through enterohepatic circulation is excreted in urine as ----------------, which gives yellow color of urine
Pre-hepatic Jaundice is caused by an increased rate of ---------------------------------------------------------------------
Physiological Jaundice in newborns occurs due to ------------------------------------------------------------------------------
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Hepatic cause of physiological jaundice in newborns ------------------------------------------------------------------------------------Kernicterus may occur in new born because ------------------------------and when ------------------------------------------
Thank you
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