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114,800 (2015) [8] Sickle cell disease ( SCD ), also simply called sickle cell, is a group of hemoglobin-related blood disorders typically inherited. [2] The most common type is known as sickle cell anemia. [2] It results in an abnormality in the oxygen-carrying protein haemoglobin found in red blood cells. [2]
Sickle cell trait describes a condition in which a person has one abnormal allele of the hemoglobin beta gene (is heterozygous), but does not display the severe symptoms of sickle cell disease that occur in a person who has two copies of that allele (is homozygous).
Photomicrograph of normal-shaped and sickle-shape red blood cells from a patient with sickle cell disease. Sickle cell anemia is a genetic disease that causes deformed red blood cells with a rigid, crescent shape instead of the normal flexible, round shape. It is caused by a change in one nucleotide, a point mutation in the HBB gene.
While malaria is still affecting the regular cells (2), the ratio of sickle to regular cells is 50/50 due to sickle cell anemia being a heterozygous trait, so the malaria cannot affect enough cells with schizonts (5) to harm the body.
Heterozygote advantage is a major underlying mechanism for heterosis, or "hybrid vigor", which is the improved or increased function of any biological quality in a hybrid offspring. Previous research, comparing measures of dominance, overdominance and epistasis (mostly in plants), found that the majority of cases of heterozygote advantage were ...
Spherocytosis is the presence of spherocytes in the blood, i.e. erythrocytes ( red blood cells) that are sphere-shaped rather than bi-concave disk shaped as normal. Spherocytes are found in all hemolytic anemias to some degree. Hereditary spherocytosis and autoimmune hemolytic anemia are characterized by having only spherocytes.
Sickle cell-beta thalassemia is caused by inheritance of a sickle cell allele from one parent and a beta thalassemia allele from the other. Mutations. A sickle allele is always the same mutation of the beta-globin gene (glutamic acid to valine at amino acid six). In contrast, beta-thalassemia alleles can be created by many different mutations ...
Anthony Clifford Allison (21 August 1925 – 20 February 2014) was a South African geneticist and medical scientist who made pioneering studies on the genetic resistance to malaria. [2] Clark completed his primary schooling in Kenya, completed his higher education in South Africa, and obtained a BSc in medical science from the University of the ...
Genetic disorder. A genetic disorder is a health problem caused by one or more abnormalities in the genome. It can be caused by a mutation in a single gene (monogenic) or multiple genes (polygenic) or by a chromosomal abnormality. Although polygenic disorders are the most common, the term is mostly used when discussing disorders with a single ...
In avian gastrulation, Koller's sickle is a local thickening of cells at the posterior edge of the upper layer of the area pellucida called the epiblast. Koller's sickle is crucial for avian development, due to its critical role in inducing the differentiation of various avian body parts. Koller's sickle induces primitive streak and Hensen's ...
