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Haemochromatosis is protean in its manifestations, i.e., often presenting with signs or symptoms suggestive of other diagnoses that affect specific organ systems.Many of the signs and symptoms below are uncommon, and most patients with the hereditary form of haemochromatosis do not show any overt signs of disease nor do they have premature morbidity, if they are diagnosed early, but, more ...
An obligate carrier is an individual who may be clinically unaffected but who must carry a gene mutation based on analysis of the family history; usually applies to disorders inherited in an autosomal recessive and X-linked recessive manner.
In medical genetics, compound heterozygosity is the condition of having two or more heterogeneous recessive alleles at a particular locus that can cause genetic disease in a heterozygous state; that is, an organism is a compound heterozygote when it has two recessive alleles for the same gene, but with those two alleles being different from each other (for example, both alleles might be ...
A heterozygote advantage describes the case in which the heterozygous genotype has a higher relative fitness than either the homozygous dominant or homozygous recessive genotype. Loci exhibiting heterozygote advantage are a small minority of loci. [1] The specific case of heterozygote advantage due to a single locus is known as overdominance.
A carrier gets a normal gene to produce hemoglobin A, from one parent and the other parent supplies a gene which makes no hemoglobin A. [6] Delta-beta thalassemia is considered rare. [2] Delta-beta-thalassemia is caused by deletions of the entire delta and beta genes sequences and only gamma-globin and HbF are formed.
Symptoms depend on the type and severity of thalassemia. Carriers of thalassemia genes may have no symptoms (thalassemia minor) or very mild symptoms with occasional crisis (thalassemia intermedia); individuals who are homozygous for the mutation have severe and life threatening symptoms (thalassemia major). [19] [20]
Normal adult hemoglobin is composed of four protein chains, two α and two β-globin chains arranged into a heterotetramer. In thalassemia, patients have defects in the noncoding region of either the α or β-globin genes, causing ineffective production of normal alpha- or beta-globin chains, which can lead to ineffective erythropoiesis ...
The significance of the sickle-cell trait is that it does not show any symptoms, nor does it cause any major difference in blood cell count. The trait confers about 30% protection against malaria [clarification needed] and its occurrence appears to have risen tremendously in Africa, India and the Middle East. Some findings also show the ...