heme and globin. Globin is made up of 4 polypeptide chains. In normal adult hemoglobin (Hb A), the predominant type of hemoglobin after the first year of life, 2 of the globin polypeptide chains are identical to one another and are designated the alpha chains. The other 2 chains are also identical to one another but differ from the alpha chains and are termed the beta chains. In fetal hemoglobin (Hb F), the predominant hemoglobin during fetal development, there are 2 alpha chains and 2 different chains called gamma chains.
The problem in the thalassemias is with globin production. The thalassemias are classified according to the type of globin polypeptide chain that is underproduced. The alpha chain is involved in alpha thalassemia (and the beta chain is affected in the more familiar beta thalassemia).
In alpha thalassemia, the heterozygous state (with a single gene for alpha thalassemia) is innocuous or harmless. There are no symptoms or at most mild anemia, because there is another gene still able to make alpha chains.
However, the homozygous state (with both genes for alpha thalassemia) is lethal before birth because no alpha chains can be made and without alpha chains, there can be no Hb F or Hb A and without Hb F or Hb A, the inevitable result is an unsuccessful pregnancy.
- Thalassemia, beta
Also known as thalassemia major .The clinical picture of this important type of anemia was first described in 1925 by the pediatrician Thomas Benton Cooley.. Other names for the disease are Cooley’s anemia and Mediterranean anemia. The name thalassemia was coined by the Nobel Prize winning pathologist George Whipple and the professor of pediatrics Wm […]
- Thalassiosira pseudonana
An ocean diatom that is a major participant in the biological pumping of carbon to ocean depths and that has potential for mitigating global climate change. The DNA of this diatom is being sequenced.
- Thalidomide baby
An infant who is affected by prenatal exposure to the drug thalidomide. In 1998, thalidomide again became available to treat certain conditions, and there is concern that babies may be born with the thalidomide syndrome as they were in the 1950s and early 1960s.
A metallic element having the symbol Tl and the atomic number 81 and an atomic weight of about 204. Approximately 70% of thallium production is used in electronics with the remaining used in pharmaceuticals, optics, infrared detectors, and nuclear medicine. Thallium was historically used as rat poison and insecticides, however due to its nonselective toxicity, […]
- Thallium poisoning
Poisoning with the element thallium which enters the environment primarily from coal-burning and smelting. It stays in the air, water, and soil for a long time and is not broken down. It builds up in fish and shellfish. The major source of exposure to thallium for most people is eating food contaminated with thallium. Other […]