Globin Information and Courses from MediaLab, Inc.
These are the MediaLab courses that cover Globin and links to relevant pages within the course.
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| Defining Thalassemia Thalassemia is best thought of as a group of disorders rather than a single disease. They demonstrate a hemoglobin synthesis disorder in which there exists a defect in the rate of production of one or more of the globin chains. This defect results from either a heterozygous or homozygous deletion or inactivation of a globin chain gene. | View Page |
| Defining Thalassemia Thalassemias are named according to the affected gene or globin chain which is showing reduced or absent synthesis. Globin chain loci are found on chromosome 11 (Beta, Delta, Epsilon, and Gamma) chromosome 16 (Alpha, and Zeta) | View Page |
| Defining Alpha Thalassemia Alpha thalassemia demonstrates problems with alpha globin chain production. One to four loci that code for the alpha chain may be deleted from chromosome 16. The greater the number of loci deleted or inactivated, the greater the severity of the anemia which develops. Many different mutations exist that result from partial deletions of alpha genes. This unit of study deals only with the forms of alpha thalassemia that have entire loci deleted. | View Page |
| Anemia in Alpha Thalassemia In thalassemia there is often an excess production or accumulation of globin chains produced by genes that are not effected by the thalassemia deletion. In alpha thalassemia this may be seen as gamma chain tetramers (hemoglobin Bart's) in the unborn child and as beta chain tetramers (hemoglobin H) in adults. Tetramer accumulation often leads to red blood cell damage and hemolytic anemia. | View Page |
| Summary The normal RBC count (4.84 x 1012/L) in this case, together with the decreased hemoglobin (8.4 g/dL) and MCV (59 fl) is an indicator of ineffective erythropoeisis that often points to thalassemia.The RBC morphology shows slight hypochromic microcytosis with codocytes, schizocytes, and basophilic stippling. Schizocytes form by several mechanisms, one being the removal of RBC inclusions.This patient's elevated bilirubin correlates with her presentation of sclera icterus; her splenomegaly is consistent with increased RBC destruction.The Hb electrophoresis demonstrated a normal pattern, initially, but the unstable Hemoglobin H was revealed upon repeat electrophoresis with reduced incubation time. Hemoglobin H is the result of beta globin chain tetramer formation due to the insufficient supply of alpha globin chains in alpha thalassemia intermedia.People with Hemoglobin H disease (alpha thalassemia intermedia) usually have a normal life expectancy without treatment. However, hemolysis may lead to moderate anemia that may be treated with splenectomy. | View Page |
| Hemoglobin Electrophoresis Theory Hemoglobin electrophoresis is the movement of hemoglobin proteins in an electric field at a fixed pH.Because the various hemoglobins are comprised of different combinations of globin chains (normal or abnormal), they will demonstrate different degrees of mobility. Typically, when a thalassemia or hemoglobinopathy is suspected, an alkaline electrophoresis is performed which may be confirmed with acid electrophoresis.For an alkaline hemoglobin electrophoresis, a hemolysate is applied to cellulose acetate which is electrophoresed in a buffer at pH 8.4-8.6. At this pH hemoglobin proteins move from cathode to anode. The proteins are visualized by the application of a dye which also makes them measurable by densitometry. | View Page |
| Defining Thalassemias Thalassemias are part of a group of hemoglobin synthesis disorders in which a defect exists in the rate of production of one or more of the globin chains. This defect results from either a heterozygous or homozygous deletion or inactivation of a globin chain gene.Thalassemias are named according to the affected gene or the globin chain that is showing reduced or absent synthesis.Globin chain loci are found on: chromosome 11 (beta, delta, epsilon, and gamma) chromosome 16 (alpha, and zeta) | View Page |
| Defining Beta Thalassemia Beta thalassemia demonstrates problems with beta globin chain production. One or two loci that code for the beta chain may be deleted from chromosome 11. The greater the number of loci deleted or inactivated, the greater the severity of the anemia which develops. Many different mutations exist that result from partial deletions of beta genes. This unit of study deals only with the forms of beta thalassemia that have entire loci deleted. Deletions of additional globin genes coded for on chromosome 11 can result in such combinations as delta-beta thalassemia. | View Page |
| Beta Thalassemia States Heterozygous states can express themselves as beta thalassemia minor, beta thalassemia intermedia, and silent carrier. The homozygous state is beta thalassemia major, though one type of beta thalassemia intermedia is caused by a homozygous state. A larger deletion on chromosome 11 results in delta-beta thalassemia, which also has heterozygous and homozygous states. | View Page |
| Anemia in Beta Thalassemia In thalassemia, there is often an excess production or accumulation of globin chains whose genes are not affected by the deletion.In beta thalassemia, this may be seen as an increase in gamma chain and delta chain production, leading to increased levels of hemoglobin F and A2 respectively.Excess alpha chains may also form tetramers which often lead to red cell membrane damage and decreased red cell deformability. This leads to a hemolytic anemia. Adding to the anemia is a decrease in the total amount of hemoglobin produced in spite of the erythroid hyperplasia of the bone marrow. | View Page |
| Thalassemia results from which of the following? | View Page |
| Hemoglobin Electrophoresis Theory Hemoglobin electrophoresis is the movement of hemoglobin proteins in an electric field at a fixed pH.Because the various hemoglobins are comprised of different combinations of globin chains (normal or abnormal), they will demonstrate different degrees of mobility. Typically, when a thalassemia or hemoglobinopathy is suspected, an alkaline electrophoresis is performed which may be confirmed with acid electrophoresis.For an alkaline hemoglobin electrophoresis, a hemolysate is applied to cellulose acetate which is electrophoresed in a buffer at pH 8.4-8.6. At this pH hemoglobin proteins move from cathode to anode. The proteins are visualized by the application of a dye which also makes them measurable by densitometry. | View Page |
| A normal hemoglobin molecule is comprised of the following: | View Page |
| Cells as shown in this iron-stained bone marrow preparation are found in each of the following conditions except: | View Page |