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Genetics Trouble > Molecular Genetics of Hemoglobinopathies > Flashcards

Molecular Genetics of Hemoglobinopathies Flashcards

1
Q

What is the major hemoglobin form/structure, and what are its subunits?

A

HbA (adult hemoglobin), alpha2beta2

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2
Q

What genes are found in the alpha cluster?

A

zeta-alpha2-alpha1

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3
Q

What chromosome is the alpha cluster on? Beta?

A

alpha: ch 16
beta: ch 11

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4
Q

how many copies of alpha genes are in the alpha cluster? Beta?

A

alpha: 2 copies
beta: 1 copy

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5
Q

What genes are found in the beta cluster?

A

epsilon-gammaG-gammaA-delta-beta

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6
Q

Is the LCR located upstream/downstream of the 2 clusters?

A

Upstream

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7
Q

Deletion of _______ causes beta-thalassemia. Result?

A

LCR of beta cluster ==> no beta globin –> ppt of alpha globin

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8
Q

How many alpha genes do we have?

A

4 (2 alleles with 2 alphas)

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9
Q

Hb gower 1 subunits (embryonic)

A

zeta2-epsilon2

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10
Q

Hb gower 2 subunits (embryonic)

A

alpha2-epsilon2

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11
Q

Hb portland subunits (embryonic)

A

zeta2-gamma2

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12
Q

HbF subunits (fetal)

A

alpha2-gamma2

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13
Q

HbA2

A

alpha2-delta2 (<3.5%)

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14
Q

How many Hb forms do adults have? Adult Hb made where?

A

2 - HbA and HbA2

made in bone marrow

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15
Q

How many Hb forms do fetus have? Fetal Hb made where?

A

1 - alpha2gamma2

made in liver

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16
Q

How many Hb forms do embryos have? Made where?

A 
3 - 
     - Hb gower I: zeta2-epsilon2
     - Hb Gower II: alpha2-epsilon2
     - Hb portland: zeta2-gamma2
made in yolk sac
17
Q

In globin switching, what genes get turned off and what genes get turned on at embryogenesis? At what location?

A

Turn off: zeta and epsilon
turn on: alpha and gamma
at alpha locus

(embryo–> fetus)

18
Q

In globin switching, what genes get turned off and what genes get turned on at birth? At what location?

A

Turn off: gamma
Turn on: beta and delta
at beta locus

(fetal –> adult)

19
Q

How much less soluble is HbS than HbA?

20
Q

What inheritance pattern is Sickle Cell Anemia?

A

Autosomal recessive

21
Q

What is the mutation in Hemoglobin C (HbCC)?

A

point mutation: Glu6Lys / E6K in beta globin gene

22
Q

What inheritance pattern is Hemoglobin C disease?

A

autosomal recessive

23
Q

What chaos does HbCC invoke in the cell?

A

HbC (like HbS) is also less soluble than HbA

it forms crystals and cause lysis of RBC

24
Q

What is a common diagnosis method for Sickle cell disease?

A

HbS diagnostic using MstII restriction enzyme in RFLP

  • normal beta globin allele gives 2 fragments
  • mutant beta globin allele gives 1 long fragment
25
Phenotype and geographical distribution of: | αα/α-
silent carrier africa, mediterranean, asia
26
Phenotype and geographical distribution of: | αα/--
mild anemia: alpha-thalassemia I | ``` Southeast Asia (-- knock out both copies on 1 chromosome) ```
27
Phenotype and geographical distribution of: | α-/α-
mild anemia: alpha-thalassemia II africa, mediterranean, asia (knock out 1 copy on each chromosome)
28
Phenotype and geographical distribution of: | α-/--
Severe anemia Southeast Asia(--)
29
Phenotype and geographical distribution of: | --/--
Hydrops fetalis Southeast Asia(--)
30
Thalassemia major - whats wrong with the genes? - phenotype?
2 absent beta globin genes or severely abnormal gene -severe anemia
31
Thalassemia Minor - whats wrong with the genes? - phenotype?
1 normal gene, 1 abnormal beta globin gene
32
What mode of inheritance is Thalassemia?
autosomal recessive
33
Beta^o thalassemia has too much/too little beta globin synthesis?
too little - 0 beta globin synthesis due to del, nonsense, fs,
34
Beta^ + thalassemia has none/some beta globin made
some due to mut affecting txn, RNA processing, prot stability
35
Alpha-thalassemia defect occurs when? (think development)
fetal and postnatal defect in alpha globin gene
36
Beta-thalassemia defect occurs when? (think development)
post natal defect only (globin switch) in beta blobin gene or LCR/beta gene cluster
37
Hereditary persistence of fetal Hb (HPFH) cause? effect?
deletion in delta and beta genes --> no delta or beta synthesis results in increased gamma globin expression
38
What subunits are present in HPFH? Phenotype?
alpha2gamma2 , disease free! No phenotype!

Genetics Trouble (10 decks)

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