Thalassemia Genetics

  1. Most prevalent adult hemoglobin has these globin subunits:
    Alpha 2 beta 2
  2. The alternative form of adult hemoglobin has these globin subunits:
    Alpha 2 delta 2
  3. Fetal hemoglobin has _____ affinity for oxygen due to its ____ subunit
    • Higher
    • Gamma
  4. Homotetramer of _____, Hb____, is observed with alpha-thalassemia
    • Beta globin (complete absence of alpha globin)
    • HbH – alpha-thalassemia
  5. Alpha thalassemia observed in fetus is also known as ___
    Hb Barts
  6. Alpha globin at chromosome ___ and non-alpha globin at chromosome ____
    • 16 (alpha)
    • 11 (non-alpha)
  7. T/F: fetal hemoglobin is present right at start of gestational period (day 0)
    • False; alpha and gamma subunits begin to form around 3 months or so
    • Embryonic is zeta and epsilon
  8. Embryonic hemoglobin:
    • Gower 1 (zeta 2 epsilon 2)
    • Portland 1 (zeta 2 gamma 2)
    • Gower 2 (alpha 2 epsilon 2)
  9. Epsilon globin _____ at the same rate as _____ globin increases, which then decreases at the same rate that ___ globin increases and is supplemented by _____ globin
    • Decreases
    • Gamma
    • Beta
    • Delta
  10. Deficiency of which globin is fatal to early embryonic stage:
    • Epsilon
    • Zeta
  11. T/F: deficiency of delta globin is usually fatal
    False; it is the alternative adult hemoglobin
  12. T/F: beta thalassemia is irrelevant prior to birth
    True; neonate is completely normal at birth with beta thalassemia and continue to be okay for 4 months after until existing fetal hgb becomes depleted
  13. Beta globin deficiency can cause insufficiency of ______ (hemoglobin tetramer), as well as an excess of ____ globin subunit
    • HbA1
    • Alpha
  14. What happens with excess alpha globin in beta-thalassemia?
    Alph globin precipitates causing damage to the RBC membrane which reduces rbc half life leading to hemolytic anemia and iron overload
  15. Betal thalassemia minor vs beta thalassemia major:
    • Minor- has one working allele (B0/B) = beta-thalassemia trait
    • Major- has no working allele = complete knockout (B0/B0)
  16. What is Cooley anemia?
    • It is beta thalassemia major – no expression of beta globin from either allele
    • It is severe life threatening anemia starting within months of birth
  17. What is beta thalassemia intermedia?
    Neither allele is the wildtype, but at lease some beta globin is expressed from at least one allele
  18. HbH and Hb Barts oxygen binding ability:
    • Bind oxygen tightly
    • Lack cooperativity
    • Act as an oxygen sinks and are harmful
  19. African pattern of alpha thalassemias vs Asian pattern of alpha thalassemia (alpha thal minor)
    • African: recombination of alpha 1 and alpha 2 genes – has one active gene at the allele
    • Asian: recombination of alpha 1 and psi gene- no active gene at the allele
  20. HgH disease is alpha thalassemia _____
    • Intermedia
    • Three out of the four alpha globin genes are deleted
  21. Hydrops fetalis is _____
    • Alpha thalassemia major
    • No a-hemoglobin is expressed- fetal
  22. Only one alpha globin is deleted, this is:
    Silent carrier alpha thalassemia
Card Set
Thalassemia Genetics
HemeOnc Midterm 2