Chapter 14 Part 6-Sickle cell disease” You tube video,7:05, Jan 2013


This video review highlighted the effects of sickle cell disease. The speaker informed where the disease is most common, which is in Africa and stated that sickle cell is an inherited disease. He only mentioned that the disease is common in Africa, however, countries such as the US have a high percentage of this blood genetic disorder. This video, therefore, mostly referred to the effects of the sickle cell trait in Africa, for example the advantage of those with the sickle cell trait is they are resistant to malaria.


I must recommend the speaker of this video for giving a detailed description of what causes sickle cell. He highlighted  a crucial point, which is the exchange of a hydrophilic amino acid with a hydrophobic amino acid in the beta chain of haemoglobin. To make his information more precise, he should have stated that haemoglobin is a protein made up of four amino acids- 2 alpha and 2 beta, giving this globular protein a quarternary structure. His way of presenting how sickle cell is inherited was commendable. It was presented in the easiest way possible, which was a punnet square. This would enable students to easily understand the concept of how it is inherited from mother/father.

A and a  represented the dominant and recessive alleles for blood in referral to inheritance of sickle cell.

The sickle cell allele shows codominance (Aa). Heterozygotes express both alleles. Those who are homozygous recessive (aa) have the disease while those with the alleles AA do not have the disease.

A cross showing two parents both possessing the trait is shown below

Aa x Aa = AA,Aa,Aa,aa

This cross tells us that two heterozygous parents would produce one offspring with no sickle cell disease, two offspring with the sickle cell trait and one with the disease.

I also came across something that was new to me relating to change in red blood cell chape

Change in red blood cell shape occurs under acidic conditions. When excercising or doing any vigorous activity, more carbon dioxide is being created from the Krebs cycle, causing blood to be more acidic. This causes the haemoglobin to change shape.

So two things I learnt from the video:

1) sickle cell trait causes resistance to malaria

2) haemoglobin shape changes in acidic conditions.

The second point was a bit confusing because it seems to me, that the speaker is saying, sickle cell can be caused by acidic conditions in the blood.

This topic was not covered in depth during my Biochemistry 1 course, but the information provided here was sufficient enough. However, for a university student investigating the disease even further, this video will not suffice.

Figure A shows normal red blood cells flowing freely in a blood vessel. The inset image shows a cross-section of a normal red blood cell with normal hemoglobin. Figure B shows abnormal, sickled red blood cells blocking blood flow in a blood vessel. The inset image shows a cross-section of a sickle cell with abnormal (sickle) hemoglobin forming abnormal strands.



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