Hemoglobin variants

Hemoglobin variants are different types of hemoglobin molecules, by different combinations of its subunits and/or mutations thereof. Hemoglobin variants are a part of the normal embryonic and fetal development. They may also be pathologic mutant forms of hemoglobin in a population, caused by variations in genetics. Some well-known hemoglobin variants, such as sickle-cell anemia, are responsible for diseases and are considered hemoglobinopathies. Other variants cause no detectable pathology, and are thus considered non-pathological variants. Some normal hemoglobin types are; Hemoglobin A (Hb A), which is 95–98% of hemoglobin found in adults, Hemoglobin A2 (Hb A2), which is 2–3% of hemoglobin found in adults, and Hemoglobin F (Hb F), which is found in adults up to 2.5% and is the primary hemoglobin that is produced by the fetus during pregnancy. Hemoglobin variants occur when there are genetic changes in specific genes, or globins, that cause changes or alterations in the amino acid. They could affect the structure, behavior, the production rate, and/or the stability of that specific gene. Usually there are four genes that code for alpha globin and two genes that code for beta globin. If the genes for alpha chains is mutated, the most common condition that occurs is alpha thalassemia, which causes a decrease in production of that gene. The level of severity of alpha thalassemia is determined by the number of genes that are affected. Hemoglobin variants are most often inherited characteristics. First, abnormal beta gene can be inherited in an autosomal recessive fashion. This means that the person who inherits this will have two copies of the altered gene. Both of these genes can be passed to offspring. The next way they can be inherited is in a heterozygous fashion. This means that the person has one normal beta gene and one abnormal beta gene. This person is considered to be a carrier of whichever hemoglobin variant is inherited. Only the abnormal gene can be passed on to offspring in this case.

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