Sickle cell disease is caused by a variant of the beta-globin gene called sickle hemoglobin (Hb S). Inherited autosomal recessively, either two copies of Hb S or one copy of Hb S plus another beta-globin variant (such as Hb C) are required for disease expression.
What causes HbS to polymerize?
The amount of HbS in red cells influences the tendency of HbS to form polymers. For example, dehydration of red cells increases the concentration of HbS and promotes sickling. The time that red cells are exposed to low concentrations of oxygen.
What caused the HbS to come into existence?
HbS arises from a mutation substituting thymine for adenine in the sixth codon of the beta-chain gene, GAG to GTG . This causes coding of valine instead of glutamate in position 6 of the Hb beta chain.
What is the mutation that created the HbS allele?
Sickle cell trait is caused by abnormal hemoglobin called sickle hemoglobin or Hb S. Sickle hemoglobin is as a result of a point mutation in the beta globin chain. This point mutation replaces A with T at codon 6 of beta hemoglobin chain.
What causes sickle cell anemia mutation?
Genetics. Sickle cell disease is caused by mutations in the beta-globin (HBB) gene that lead to the production of an abnormal version of a subunit of hemoglobin — the protein responsible for carrying oxygen in red blood cells. This mutated version of the protein is known as hemoglobin S.
How long can a person live with sickle cell disease?
With a national median life expectancy of 42–47 years , people with sickle cell disease (SCD) face many challenges, including severe pain episodes, stroke, and organ damage.
What blood type carries sickle cell?
It is an inherited condition in which both hemoglobin A and S are produced in the red blood cells, always more A than S. Individuals with sickle cell trait are generally healthy.
What is the function of HbS?
The function of haemoglobin is to carry oxygen from the lungs to all parts of the body . Because of their shape, sickled red blood cells can't squeeze through small blood vessels as easily as the almost donut-shaped normal cells.
What is the difference between HbA and HbS?
The b chain of hemoglobin is dark grey. The heme groups are yellow. The total solvent exposed surface area of the b subunit in Hb A is 23476 A ̊ 2 and 23246 A ̊ 2 in HbS which is a difference of approximately 1% . The structure of the mutant HbS and wild type HbA are very similar as determined by X-ray diffraction.
What will reduce HbS polymerization?
Polymerization (left) can be averted by (1) increasing HbF levels; (2) increasing hemoglobin-oxygen affinity, as with voxelator; (3) “ rehydrating” the sickle cell , thereby decreasing the concentration of HbS.
Why is sickle cell more common in Africa?
Researchers found that the sickle cell gene is especially prevalent in areas of Africa hard-hit by malaria . In some regions, as much as 40 percent of the population carries at least one HbS gene.
Is HbS a gene?
Sickle cell disease is caused by a variant of the beta-globin gene called sickle hemoglobin (Hb S). Inherited autosomal recessively, either two copies of Hb S or one copy of Hb S plus another beta-globin variant (such as Hb C) are required for disease expression.
What are the normal and sickle cell alleles called?
Genetics. 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 sickle cell trait inherits one normal allele and one abnormal allele encoding hemoglobin S (hemoglobin genotype AS).
What are the 4 types of mutation?
- Germline mutations occur in gametes. Somatic mutations occur in other body cells.
- Chromosomal alterations are mutations that change chromosome structure.
- Point mutations change a single nucleotide.
- Frameshift mutations are additions or deletions of nucleotides that cause a shift in the reading frame.
Is Sickle Cell curable?
Stem cell or bone marrow transplants are the only cure for sickle cell disease , but they're not done very often because of the significant risks involved. Stem cells are special cells produced by bone marrow, a spongy tissue found in the centre of some bones. They can turn into different types of blood cells.
Who is most at risk for sickle cell anemia?
Risk Factors
Sickle cell disease is more common in certain ethnic groups, including: People of African descent , including African-Americans (among whom 1 in 12 carries a sickle cell gene) Hispanic-Americans from Central and South America. People of Middle Eastern, Asian, Indian, and Mediterranean descent.
