Sickle cell, Biology

Sickle cell anaemia in man is caused by a defective chain of haemoglobin. The abnormal haemoglobin known as MbS differs from natural haemoglobin (HhA) in one amino acid. A substitutional mutation causes the replacement of glutamic acid by valine in the sixth position from the amino terminal end of the Q chain polypeptide. This is because instead of the triplet GAA or GAG which codes for glutarnic acid in normal chains, the abnormal mRNA has GUA or GUG which codes for valine. IdbS in deoxygenated state precipitates out of solution forming elongate crystals. 'The formation of crystals in turn produces a characteristic deformation of RBCs and the cells acquire a crescent or sickle shape, hence the name sickle cell anaemia. The deformation of red cell weakens the red cell membrane and lyses the cells. The loss of red cells and haemoglobin leads to anaemia and this causes oxygen deficiency to the tissues per unit time. Pt, single substitution, more specifically, replacing the thymine by adenine in the second position of the sixth triplet of the P chain gene triggers a variety of responses that affects several aspects of the pfnysiology of the organism. Individuals who are homozygous (HbSiHbS) for the gene usually die early in life. In heterozygotes some proporrion of red cells lyse periodically but this does not cause any serious harm to the individual and in any case the survival is not affected.

Posted Date: 4/6/2013 1:20:00 AM | Location : United States







Related Discussions:- Sickle cell, Assignment Help, Ask Question on Sickle cell, Get Answer, Expert's Help, Sickle cell Discussions

Write discussion on Sickle cell
Your posts are moderated
Related Questions
Normal 0 false false false EN-IN X-NONE X-NONE MicrosoftInternetExplorer4 Mode of feeding

WHAT IS THERE BETWEEN THE TRACHEA OF COCKROACH AND RABBIT

Q. What hormone can be used to overcome jet lag? Jet lag takes place when an individual's biological clock is out of sync with local time. According to general rule it takes ab

A cellular system has a total of 500 duplex voice channels. The service area is divided into 150 cells. Suggest a three different cluster size (N) values. In each case, determine

The fact that some pure solutions of hydrocarbons do not readily evaporate at room temperature is a result of Select one: a. London dispersion forces. b. The hydrophobic effe

Indications For Surgery :  The normal aortic valve area in the adult is about 3-4 cm2. Significant symptoms occur when the valve area is seduced to 1/4"' the normal area

What are the stomata? How these structures participate in the plant transpiration? The Stomata (singular, stoma) are small specialized passages for gases and water present in t

Comparison of CABG and Angioplasty :  Results of six major randomized clinical trials of multi vessel angioplasty Vs CABG are now available. The main conclusions are: Patient

What are some biological examples in which lysosomic enzymes play a fundamental role? The remodelation of the osseous tissue, the function of acrosomes in sperm cells and the e

Q. As per the Watson - Crick Model how many polynucleotide chains does a DNA molecule have? The DNA molecule is formed by two polynucleotide chains bound in antiparallel mode (