ORGANIZATION OF THE GLOBIN GENES Flashcards
is located on chromosome 16, and it contains three genes: ζ, α2, and α1.
α-Gene family:
is only expressed in fetal life,
ζ (zetta) genes
are expressed in both fetal life and adulthood
α2 and α1 genes
A single gene for the β-globin chain is located on chromosome 11 .
β-Gene family:
additional four β-globin-like genes:
ε (epsilon) gene, two γ (gamma) genes, δ (delta)gene
caused by production of a structurally abnormal hemoglobin molecule; synthesis of insufficient quantities of normal hemoglobin; or, rarely, both
Hemoglobinopathies
the most common of the RBC sickling diseases
caused by a single nucleotide substitution in the gene for β-globin.
it is the most common inherited blood disorder in the United States.
SICKLE CELL ANEMIA ( HGB S DISEASE)
is a hemoglobin variant that has a single amino acid substitution in the sixth position of the β-globin chain.
Hemoglobin C disease
some β-globin chains have the sickle cell mutation, whereas other β-globin chains carry the mutation found in HbC disease. Patients with HbSC disease are doubly heterozygous.
Hemoglobin SC disease
(cannot bind O2)
Formed by oxidation of the heme iron in hemoglobin to the ferric (Fe3+) state.
“Chocolate cyanosis”
METHEMOGLOBINEMIAS
are hereditary hemolytic diseases in which an imbalance occurs in the synthesis of globin chains. they are the most common single gene disorders in humans.
THALASSEMIAS
synthesis of β-globin chains is decreased or absent, typically as a result of point mutations that affect the production of functional mRNA.
β-Thalassemias:
if they have only one defective βglobin gene.
make some β chains, and usually do not require specific treatment.
β-thalassemia trait (β-thalassemia minor)
if both βgenes are defective.
become severely anemic
β-thalassemia major (Cooley anemia)
synthesis of α-globin chains is decreased or absent, typically as a result of deletional mutations.
α-Thalassemias:
