| haemoglobin Gower-2 | A normal Hb of molecular formula a2A&vepsilon;2, which is a major Hb component of the early embryo; production of &vepsilon; chains normally ceases at about the third month of foetal development and is replaced by Hb F. Compare: haemoglobin Gower-1, haemoglobin Portland. (05 Mar 2000) |
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| haemoglobin H | <haematology> Haemoglobin H is an abnormal version of the protein haemoglobin. The normal haemoglobin is composed of two alpha and two beta polypeptide chains, haemoglobin H is composed of four beta chains. The molecule has a very high affinity to oxygen, but is very inefficient at transporting it. (09 Oct 1997) |
| haemoglobin I | An abnormal Hb with a single a chain substitution, molecular formula a216Lys→Glub2A; a thalassaemia-like syndrome has been found in individuals heterozygous for both Hb I and alpha-thalassaemia genes, with formation of about 70% Hb I. (05 Mar 2000) |
| haemoglobin J | <chemical> A group of abnormal haemoglobins with similar electrophoretic characteristics. They have faster electrophoretic mobility and different amino acid substitutions in either the alpha or beta chains than normal adult haemoglobin. Some of the variants produce haematologic abnormalities, others result in no clinical disorders. Chemical name: Haemoglobin J (12 Dec 1998) |
| haemoglobin JCapetown | An abnormal Hb with a single a chain substitution, molecular formula a292Arg→Glnb2A; heterozygotes have polycythemia because of increased oxygen affinity of this Hb. (05 Mar 2000) |
| haemoglobin Kansas | An abnormal Hb of molecular formula a2Ab2102Asn→Thr; found in association with familial cyanosis due to decreased oxygen affinity of this Hb. (05 Mar 2000) |
| haemoglobin M | <chemical> A group of abnormal haemoglobins in which amino acid substitutions take place in either the alpha or beta chains but near the haem iron. This results in facilitated oxidation of the haemoglobin to yield excess methemoglobin which leads to cyanosis. Chemical name: Haemoglobin M (12 Dec 1998) |
| haemoglobin Portland | A form of embryonic haemoglobin containing the ζ chains of haemoglobin Gower-1 and the g chains of Hb F, thus having the formula ζ2g2; essentially disappears by the third month of pregnancy. Compare: haemoglobin Gower-1, haemoglobin Gower-2. (05 Mar 2000) |
| haemoglobin Rainier | An abnormal Hb of the molecular formula a2Ab2145Tyr→Cys; heterozygotes have polycythemia because of increased oxygen affinity of this Hb. (05 Mar 2000) |
| haemoglobin S | <haematology> Haemoglobin S is an abnormal version of the protein haemoglobin. The sixth amino acid of the normal beta chain, glutamic acid, is replaced by valine with gluconic acid. This mutation causes the red blood cell to take on a sickle shape, and is the cause of the sickle cell trait condition (when the individual is heterozygous for this mutant haemoglobin) and the disease of sickle cell anaemia (when the individual is homozygous for this mutant haemoglobin). (09 Oct 1997) |
| haemoglobin SC disease | <disease, haematology> A rare genetic disease of the haemoglobin. Consists of two abnormal haemoglobins: s and C. Estimated prevalence to be 0.04 to 0.13% in the African American population. Patients are anemic due to the premature breakdown of the blood cells in the spleen. Produces a sickle cell-like syndrome. Jaundice may be seen in some patients. Complications include thromboembolic disease, renal papillary necrosis, aseptic necrosis of the femoral (and humeral) head, increased rates of early spontaneous abortion (in pregnant women with SC disease) and proliferative retinopathy. There is no specific treatment other than supportive care. (27 Sep 1997) |
| haemoglobin, sickle | An abnormal haemoglobin resulting from the substitution of valine for glutamic acid at position 6 of the beta chain of the globin moiety. The heterozygous state results in sickle cell trait, the homozygous in sickle cell anaemia. (12 Dec 1998) |
| haemoglobin Yakima | An abnormal Hb of the molecular formula a2Ab299Asp→His; heterozygotes have polycythemia because of increased oxygen affinity of this Hb. (05 Mar 2000) |
| hereditary persistence of foetal haemoglobin | <haematology> Hereditary persistence of foetal haemoglobin is a genetic condition where adult types of haemoglobin fail to develop and the types of haemoglobin the individual had as a foetus remains present well past the point when they would normally have stopped being produced. (09 Oct 1997) |
| sickle cell haemoglobin | <haematology> Haemoglobin S is an abnormal version of the protein haemoglobin. The sixth amino acid of the normal beta chain, glutamic acid, is replaced by valine with gluconic acid. This mutation causes the red blood cell to take on a sickle shape, and is the cause of the sickle cell trait condition (when the individual is heterozygous for this mutant haemoglobin) and the disease of sickle cell anaemia (when the individual is homozygous for this mutant haemoglobin). (09 Oct 1997) |