Hb and Hb genes

Question 1

structure of adult Hb /fetal Hb ?

2

Answer 1

-Quaternary Compex
-Adult Hb: 2xalpha / 2xBeta
-Fetal Hb: 2xAlpha/2xGAMMA chains
4x Heme groups ( perforin group+Fe2+)

Question 2

why does Fetal Hb have a higher affinity for O2, why?
(4)
shift?

Answer 2

• Shift to LHS on oxygen dissociation curve(ODC)
• Fetal haemoglobin contains 2 gamma chains which are less positively charged than the Beta chain in adult Hb = fetal haemoglobin is more negatively charged
• the chemical (negative charged ) 2,3-BPG = makes O2 dissociate from Hb =decreases affinity for O2 = not present in fetal haemoglobin

-2,3BPG = more attracted to ADULT HB, with BETA chains, so the fetal Hb has more affinity for Oxygen ( because 2,3 BPG isn’t present )
negative, negative repel more

Question 3

What happens in Sickle cell Anemia ?

5

Answer 3

• point mutation in HbS Beta chain
• adenine changes to Thymine
• 6th AA=> Glu–>Val this means the side chain which is polar changes to a hydrophobic chain
• this leads to a conformational change = Sickle cell shape
• this block Capillaries , shorter life span of cells , sickle shaped cells destroy the spleen (spenomegaly), anemia , bone marrow can run into OVERDRIVE=HYPERPLASIA
• Autosomal recessive

Question 4

what are the Hb gene families and where are they found ?
(2)
Types of Hb ?

Answer 4

-chromosome 16
-chromosome 11
Many Types of Hb:
HbF
HbA
HbS= sickle cell Anemia

Question 5

what can happen with mutations in the gene coding for HB?

2

Answer 5

1) Altered AA, altered Hb, sickle cell

2) defective regulation Hb regulation =altered ratio of chains ,altered properties of Hb