HAEMOGLOBIN GENOTYPE : HAEMOGLOBIN GENOTYPE
The oxygen-carrying protein hemoglobin was discovered by Hünefeld in 1840. Then in 1851, Otto Funke published a series of articles in which he described growing hemoglobin crystals by successively diluting red blood cells with a solvent such as pure water, alcohol or ether, followed by slow evaporation of the solvent from the resulting protein solution.
Hemoglobin’s reversible oxygenation was described a few years later by Felix Hoppe-Seyler. Max Perutz in 1959 determined the molecular structure of hemoglobin by X-ray crystallography. This work resulted in his sharing with John Kendrew the 1962 Nobel Prize in Chemistry.
The role of hemoglobin in the blood was elucidated by physiologist Claude Bernard 1973. The name hemoglobin is the portmanteau of heme and globin, reflecting the fact that each subunit of hemoglobin is a globular protein with an embedded heme (or haem) group. Each heme group contains one iron atom, that can bind one oxygen molecule through ion-induced dipole forces (Bunn, 1997)
The iron in haemoglobin is often thought to account for the distinctive red colouration of our blood, in the same way that iron oxide gives rust its colour. As it happens, here the iron content is just a coincidence - the red colouration in fact comes from the porphyrin (the word 'porphyrin' derives from a Greek word for a reddish purple). Just how red the haemoglobin is, depends on whether there is oxygen bound to it. When there is oxygen present, it changes the shape of the porphyrin, making the colour a brighter red (Clegg, 2000).
There are also different forms of haemoglobin that can cause illness. Sickle cell anaemia, for example, is caused by an abnormal haemoglobin structure, which reduces the oxygen carried in a red blood cell and alters its shape to the distinctive crescent moon form (Max Perutz, 1959).
The genotype of every individual means the genetic makeup of the individual. This genotype depends on the gene which is inherited from one or both parents. (Ochei 2008).
Gene is the basic unit of hereditary, it is therefore responsible for the transfer of hereditary characteristics from one generation to another, it composes the RNA and DNA sequence. (Ochei 2008).
The haemoglobin genotype is determined by the type of haemoglobin gene which an individual inherits from both parents at conception time. The haemoglobin inheritance is gotten from both parents and it follows normal mendellian theory. Every individual receives two sets of genes one from the female parent (through the egg) and the other from the male parent (through the sperm) these genes are contained in the chromosomes transmitted from the parent to the offspring, and these genes are responsible for the genotype of an individual. (Taylor D, 1998).
A normal human adult possess the HbAA genotype which means that two Hb A gene are inherited from one of each parents. There are also other haemoglobin genes, which includes Hbs S, C, D, E with other rare types. The Hb D and E gene are rare in this part of the world, but predominant in the middle east population. An individual can inherit any of these gene from either parents, and may have possible combination of any of the two of these genes.
An individual may inherit HbA gene from the father, HbS gene from the mother, such individual will have the HbAS genotype a condition known as Sickle cell trait. It is also possible for an individual to inherit the same genes from both parents, for example inheriting the Hb S gene from both father and mother, such individual will present with the HbSS genotype a condition known as sickle cell disease.(Garson AA, 2006).
Haemoglobin genotype should therefore always be the most important pre-marital tests to enable intending couples know the possible genotype which their offsprings would bear. This premarital test has really helped in recent years to reduce the number of children who die from sickle cell disease each year in Africa.(Fleming et al.,2000).