Patients with sickle cell anaemia have an altered base sequence. (Coding stand not shown) GTAGATTGGGGTCACCTC    <------- Template strand Analyse the code to discover the change. Describe the effect of this change on haemoglobin structure and function.

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GTA GAT TGG GGT CAC CTC      [Sickle Cell Anemia]

GTA GAT TGG GGT CTC CTC      [Normal hemoglobin]

CAT CTA ACC CCA GAG GAG      [Template Strand]

     When examining the template strand and the normal sequence everything matches up appropriately.  Compare the difference between the two normal and sickle cell strands and you'll notice in the sickle cell second to last triplet there is a coding error.  The template strand has GAG and normal response is CTC; however, the sickle cell shows CAC.  The coding error is across this triplet where the original A is carried over and not transcribed.

     This transcription error causes the person to produce Hemoglobin S blood.  If both parents give the hemoglobin S trait, the child will have Sickle Cell Anemia, the most severe form of Sickle Cell Disease.

     In normal hemoglobin there is a round disc-like shape which allows them flexibility traveling through the body.  Sickle cell has a convex rigid structure which does not allow for flexibility and can clog arteries.  In addition the shape does not allow for proper oxygen transfer to the cell.  This results in a lack of oxygen and can cause severe pain, called pain crises.  It can evolve into chronic pain later in life. 

     Additionally, hemoglobin S is much less stable.  Regular blood cells have a life of about 90-120 days before they hemolyze and must be replaced.  Sickle cells last only 10-20 days requiring the body to keep up with production.  This results in lower red blood count and fatigue or anemia.

      

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