Normally, a person inherits two copies of the gene that produces beta-globin, a protein needed to produce normal hemoglobin (hemoglobin A, genotype AA). A person with<unk>  inherits one normal allele and one abnormal allele encoding hemoglobin S (hemoglobin genotype AS). The<unk>  can be used to demonstrate the concepts of co-dominance and incomplete dominance. An individual with the<unk>  shows incomplete dominance when the shape of the red blood cell is considered. This is because the<unk> ng happens only at low oxygen concentrations. With regards to the actual concentration of hemoglobin in the circulating cells, the alleles demonstrate co-dominance as both 'normal' and mutant forms co-exist in the bloodstream. Thus it is an ambiguous condition showing both incomplete dominance and co-dominance. Unlike the<unk> ,<unk> -cell disease is passed on in a recessive manner.<unk>  cell anemia affects about 72,000 people in the United States. Most Americans who have<unk>  cell anemia are of African descent. The disease also affects Americans from the Caribbean, Central America, and parts of South America, Turkey, Greece, Italy, the Middle East and East India.<unk> -cell disease and the associated<unk>  are most prevalent in Africa and Central America, which is attributed to natural selection: the<unk>  confers a survival advantage in areas with a high occurrence of malaria, which has a high death rate among individuals without the<unk> . There also have been studies that show changes in the globin genes. There have been noted changes in the beta-globin sequence, to what is known as the<unk>  hemoglobin. The significance of the<unk>  is that it does not show any symptoms, nor does it cause any major difference in blood cell count. The<unk>  confers about 30% protection against malaria and its occurrence appears to have risen tremendously in Africa, India and the Middle East. Some findings also show the reduction of the<unk>  in those who retain much more fetal hemoglobin than usual in adulthood. Fetal hemoglobin likely plays a role in the prevention of<unk> ng. Elevated fetal hemoglobin levels have been observed in populations where<unk> -cell disease is prevalent. Whole genome sequence analysis has identified a single origin of the<unk><unk> , with one haplotype ancestral to all<unk> -cell variants. This haplotype is thought to have originated in the Sahara during the Holocene Wet Phase around 7,300 years ago.<unk>  cell variants descended from this ancestral haplotype comprise five haplotypes named after toponyms or ethnolinguistic groups (the Arabian/Indian, Benin, Cameroon, Central African Republic/Bantu, and Senegal variants), and another designation earmarked for atypical<unk> -cell haplotypes. Their clinical importance is because some are associated with higher HbF levels (e.g., Senegal and Saudi-Asian variants tend to have milder disease).
Sickle cell trait
Sickle cell disease
Sick cell syndrome
Hereditary spherocytosis
Paroxysmal nocturnal hemoglobinuria
EEM syndrome
Primary hyperoxaluria
Hemoglobinemia