Monday, August 20, 2012

STPM Biology - chapter 17: Revision essay question 4

4. Using a named example, describe how a gene mutation may affect a phenotype of an organism.

Answer


An example of gene mutation is sickle-cell anaemia, where there is substitution of a base thymine by adenine.in the gene that codes for the beta polupeptide chain. Sickle-cell anaemia patients have abnormal haemoglobin molecules with valine instead of glutamic acid as the sixth amino acid for both the beta-polypeptide chains.
A sickle-cell haemoglobin easily crystallize at low concentrations of oxygen and the red blood cells are pilled into a sickle shape. These sickle red blood cell can easily break and clump together to clog the blood capillaries, impeding the flow of blood. This results in less oxygen is transported to the muscles and the internal organs. Sickle-cell patients usually suffer from heart problem, kidney failure, abdominal pains, paralysis and premature death.



Assignment submitted by L.Y., Kong,  S. H., Lim, S. C., Soo, C. W.

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