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PASG 60100 Genetics > Sickle Cell Disease Ch. 11 > Flashcards

Sickle Cell Disease Ch. 11 Flashcards

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1
Q

What is the genetic cause of Sickle Cell Disease?

A

point mutation in hemoglobin beta gene (HBB) = substitution of valine for glutamine in B subunit of Hb

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2
Q

What does the point mutation in HBB gene lead to?

A

new property of Hb alters its solubility in blood especially in deoxygenated state or low pH | ability to bind to O2 unaffected

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3
Q

Define: heterozygote advantage

A

a mutated allele at same locus as normal allele = advantage of protection against a disease = increases survival

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4
Q

What heterozygote advantage does sickle cell RBCs provide?

A

sickle shape makes it difficult for malaria parasites to attach onto RBCs

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5
Q

What is the inheritance pattern of Sickle Cell disease?

A

autosomal recessive

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6
Q

How to sickle cell RBCs take shape?

A

in hypoxia = Beta-Val-6 of deO2 HbS binds to hydrophobic pocket on adjacent deO2 HbS molecule = join together = form insoluble polymer –> sickle cell shape

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7
Q

What physiological issue does sickle cell RBC shape pose?

A

aggregate sickle cells –> occlude/block vessels –> pain –> infarct tissues/cells

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8
Q

Sickle cell trait

A

heterozygous state of the gene for Hb S in sickle cell anemia.

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9
Q

Hemoglobin SC disease

A

individual has one copy of the gene for sickle cell disease and one copy of the gene for hemoglobin C disease.

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10
Q

Hemoglobin C disease

A

characterized by episodes of abdominal and joint pain, splenomegaly, mild jaundice; no severe crises | occurs mostly in African Americans, who may show few symptoms

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11
Q

How does a genetic modifier affect an HbS trait individual?

A

can induce expression of trait in carrier individual

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12
Q

What is compound heterozygosity?

A

2 different mutations (1 on each allele) for 1 gene = exacerbates issue

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13
Q

What test would you use to determine if a gene has compound heterozygosity?

A

PCR = to know specifically what the code was

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14
Q

What happens if an HbS carrier has compound heterozygosity?

A

can make a carrier look affected | “dominant” in presentation but “recessive” in inheritance model

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15
Q

What is apparent heterozygosity in sickle cell carriers?

A

If locus control for HbA is not working properly but locus control for HbS is working properly = HbS will phenotypically take over

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16
Q

What is novel property mutation?

A

mutation that gives protein product a new property (ie: shape change in HbS protein)

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17
Q

Compare normal RBC shape with sickle cell RBC shape.

A

normal = flexible and can squeeze through vessels | sickle cell = rigid and sticky = can aggregate and cause blockage

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18
Q

Compare normal RBC shape with sickle cell RBC shape.

A

normal = flexible and can squeeze through vessels | sickle cell = rigid and sticky = can aggregate and cause blockage

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19
Q

What is a sickle cell crisis?

A

acute onset | severe abd pain, stroke, priapism, acute chest syndrome, renal necrosis

20
Q

What leads to a sickle cell crisis?

A

multiple occlusions

21
Q

What is hemolytic anemia?

A

RBC lysis causing less RBCs circulating = anemia

22
Q

How does sickle cell disease lead to hemolytic anemia?

A

sickle cell RBCs get pulled out of circulation for degradation at a faster rate than normal RBCs = less RBCs circulating –> anemia

23
Q

Compare normal RBC shape with sickle cell RBC shape.

A

normal = flexible and can squeeze through vessels | sickle cell = rigid and sticky = can aggregate and cause blockage

23
Q

What is vaso-occlusion?

A

microcirculation is blocked by sickled RBCs –> ischemic injury to the organ supplied = pain

24
Q

What is ischemia?

A

lack of O2

25
Q

What is infarction?

A

death of tissue

26
Q

How can you treat ischemic tissues?

A

gradual re-perfusion of tissues

27
Q

How does sickle cell disease develop in affected newborns? At what age?

A

5mos = HbF levels drop and are replaced with rising levels of HbS

28
Q

What is a serious symptom of sickle cell disease in a newborn?

A

failure to thrive = changes in growth and development

29
Q

What is acute chest syndrome?

A

vascular occlusion and inflammation affect small vessels of the bronchial tree

30
Q

What are some signs and symptoms of acute chest syndrome?

A

(varies w/ patients) pain, respiratory illness, fever, and shortness of breath

31
Q

What is the leading cause of death among adult patients with sickle cell disease?

A

acute chest syndrome

32
Q

What test would you use to determine if someone has trait for sickle cell disease?

A

PCR and Hb electrophoresis

33
Q

How does Hemoglobin electrophoresis work?

A

get proteins from RBC cell –> put on gel –> it separates by size and charge –> observe migration pattern compared to normal (control) sample

34
Q

What is an allozyme?

A

proteins with different migration patterns on gel electrophoresis

35
Q

What factor helps malaria parasite better bind to RBC?

A

increase O2 saturation

36
Q

Ethnic variation of allelic frequency

A

frequency of mutated alleles is higher among certain ethnic groups than others.

37
Q

Compare normal RBC shape with sickle cell RBC shape.

A

normal = flexible and can squeeze through vessels | sickle cell = rigid and sticky = can aggregate and cause blockage

37
Q

What factor helps malaria parasite better bind to RBC?

A

increase O2 saturation

38
Q

What are the 3 treatments for sickle cell disease? Which are cures?

A

Hydroxyurea = treatment | CRISPR and allogenic stem cell transplant = cure

39
Q

Compare normal RBC shape with sickle cell RBC shape.

A

normal = flexible and can squeeze through vessels | sickle cell = rigid and sticky = can aggregate and cause blockage

40
Q

What are the 3 mechanisms does Hydroxyurea work to treat sickle cell disease?

A

lowers WBC count = decrease inflammatory process | metabolizes nitric oxide = vasodilates = increase blood flow | induces HbF (fetal Hb) production that is resistant to sickling

40
Q

What factor helps malaria parasite better bind to RBC?

A

increase O2 saturation

41
Q

What factor helps malaria parasite better bind to RBC?

A

increase O2 saturation

41
Q

Compare normal RBC shape with sickle cell RBC shape.

A

normal = flexible and can squeeze through vessels | sickle cell = rigid and sticky = can aggregate and cause blockage

PASG 60100 Genetics (16 decks)

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