Sickle-cell trait

In certain reglon.s of Africa, tire. sickle-cell trait Is found In 20% of the people. Wiry does snch a deleterious heritable condition persist in dre popnladon For reasons as yet unknown, individnals widr this trait are less sn.scepdble to dre most virnlent form of malaria. The geographic distribn-don of malaria and dre sickle-cell trait are posidvely correlated. 

The detection of restriction fi agment length polymorphisms (RFLPs) facilitates prenatal detection of hereditary disorders such as sickle cell trait, beta-thalassemia, infant phenylketonuria, and Huntington s disease. Detection of RFLPs involves cleavage of double-stranded DNA by restriction endonucleases, which can detect subtle alterations in DNA that affect their recognized sites. Chapter 40 provides further details concerning the use of PCR and restriction enzymes for diagnosis. 

O Sickle cell disease is an inherited disorder caused by a defect in the gene for hemoglobin. Patients may have one defective gene (sickle cell trait) or two defective genes (sickle cell disease). 

Sickle cell trait (SCT) is the heterozygous form (HbAS) of SCD in which a person inherits one normal adult hemoglobin (HbA) gene and one sickle hemoglobin (HbS) gene. These individuals... 

FIGURE 65-1. Sickle gene inheritance scheme for both parents with sickle cell trait (SCT). A, normal hemoglobin S, sickle hemoglobin. Possibilities with each pregnancy 25% normal (AA) 50% SCT (AS) 25% sickle cell anemia (SS). (From Chan CYJ, Moore R. Sickle cell disease. In DiPiro JT, Talbert RL, Yee GC, et al, (eds.) Pharmacotherapy A Pathophysiologic Approach. 6th ed. New York McGraw-Hill 2005 1856.)... 

TABLE 65-1. Clinical Features of Sickle Cell Trait and Sickle Cell Disease... 

Mother with sickle cell trait father with sickle cell disease. Father died at age 36 from stroke. Has an older brother with SCD and a younger sister with SCT. 

The most common abnormal hemoglobin in the United States is hemoglobin S (HbS). Two genes for HbS result in sickle cell disease (SCD) or sickle cell anemia, which occurs in 0.3% of African Americans. One gene for HbS results in sickle cell trait, which occurs in 8% of African Americans. Hemoglobin C, another abnormality, occurs in 2% to 3% of African Americans. 

Sickle cell trait Sickle cell anemia Sickle cell hemoglobin C... 

Patients with sickle cell trait are usually asymptomatic, except for rare painless hematuria. 

The answer is B. Sickle cell anemia is caused by inheriting two copies of a mutant P glo-bin gene that leads to synthesis of sickle hemoglobin, HbS. A severe case of sickle cell anemia would most likely have demonstrated symptoms and been diagnosed before the age of 6. However, he may only be a carrier, with one copy each of normal P-globin and one of the sickle allele, a condition called sickle cell trait. Nevertheless, the patient s... 

Sickle-cell anemia, as we have noted, occurs in individuals homozygous for the sickle-cell allele of the gene encoding the )3 subunit of hemoglobin. Individuals who receive the sickle-cell allele from only one parent and are thus heterozygous experience a milder condition called sickle-cell trait only about 1% of their erythrocytes become sickled on deoxygenation. These individuals may live completely normal lives if they avoid vigorous exercise or other stresses on the circulatory system. 

ASO probes used to detect the sickle cell mutation and differentiate between sickle cell trait and disease. 

Deficiency of the first enzyme of the pentose phosphate pathway, glucose 6-phosphate dehydrogenase, is widespread.11 Its geographical distribution suggests that, like the sickle-cell trait, it confers some resistance to malaria. A partial deficiency of 6-phosphogluconolactonase (Eq. 17-12, step b) has also been detected within a family and may have contributed to the observed hemolytic anemia.1... 

As can be seen, the codons for glutamic acid (GAA and GAG) are very similar to two of the codons (GUA and GUG) for valine. Replacement of adenine in the glutamic acid codons by uracil causes valine to be incorporated into hemoglobin instead of glutamic acid and is responsible for the sickle cell trait. 

Schneider, R. G., and Galveston, T., Incidence of Hemoglobin C trait in 505 normal negroes a family with homozygous hemoglobin C and sickle cell trait union. J. Lab. Clin. Med. 44, 133 (1954). 

Couples who each have sickle cell trait have three children none of their children have sickle cell disease.They tell you they do not want to have another child because they know there is a one in four possibility for their children to have sickle cell disease, and they already have three unaffected children. What is the probability their next child will have sickle cell disease If they have another child and this child has sickle cell disease, then what is the probability that one of the other children will be an HLA match ... 

Sickle cell trait Rare painless hematuria normal Hb level heavy exercise under extreme... 

As a result of impaired antioxidant activity in erythrocytes, there may be increased fragility of erythrocyte membranes or reduced membrane fluidity. As in sickle cell trait, which also protects against malaria, this may result in ... 

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