Sickle Cell Disease -

8/9/2019 Sickle Cell Disease -

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Sickle Cell Anemia


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What is Sickle Cell

Anemia Most common form of Sickle Cell Disease (SCD) Hereditary blood disorder abnormality inhemoglobinmolecule inred blood cells

Hemoglobintransports oxygen from respiratoryorgans to the rest of the body.

Normal hemoglobin (hemoglobin A) replaced bysickle hemoglobin (hemoglobin S).


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Normal Red Blood Cells Abnormal Red Blood Cells

Instead of donut-shaped cells sickle-shaped cells

Sickle cells block bloody flow in blood vessels

Lack of red blood cells die after 10-20 days (vs. 120 days)


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Incidence

Most commonly inherited blood disorder inthe US

Over 2 million Americans arecarriersof

SCD70,000-80,000affectedAmericans

Highest incidence rate in African-Americans when compared to otherethnicities.

1 out of 350 areaffected

1 in 12 arecarriers


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Incidence

NOT only people of African ancestry butalso of Mediterranean, Middle Eastern,Indian ancestry, and people from the

Caribbean and parts of Central and SouthAmerica.

1 out of 36,000 Hispanic-American births

areaffectedand 1 in 100 arecarriers.


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Symptoms

Present at birth

Most common are anemia and pain

Hand-foot syndrome

Frequent infections Delayed Growth

Vision Problems

Symptoms can vary per person


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When to see a doctor?

Unexplained episodes of severe pain

Swelling in the hands or feet

Abdominal swelling

Fever Pale skin or nail beds

Yellow tint to the skin or whites of the eyes

Any signs or symptoms of stroke


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Treatment

No widely available cure

Bone marrow transplant (onlypotential cure)

Aimed at avoiding crises,relieving symptoms andpreventing complications

Medications to reduce pain

are available Blood transfusions andsupplemental oxygen


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Testing

Blood Test can check for hemoglobin S

If negativeno sickle cell gene present

If positivefurther tests are done todetermine if there are one or two sicklegenes present

Can be done before birth through samplingfluid surrounding the unborn baby in thewomb

With good health care, many people whohave sickle cell anemia can live productivelives and today are living into their fortiesand fifties


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Gene

Mutation on hemoglobin-Beta gene.

The allele responsible is in the short arm of chromosome 11.

6thamino acid (glutamic acid) replaced by valine andchanges thefunction.

Known mutation of asingle nucleotide (A to T). CTC codonCAC codon which is transcribed from thetemplate strand into a GUG codon.


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Inheritance Pattern

Autosomalrecessivepattern of inheritance.

Incarriers(heterozygous Rr) problems areminor normal allele produces over 50% of

the hemoglobin. Symptoms only if deprived oxygen.


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Retrieved from the National Heart, Lung and BloodInstitute website

Rr

Rr Rr

Rr Rr

RrRr RrRr RrRr

Rr Rr

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rr rr

rrrrrrrrRR

RR RR

RR

RRrr

rr

rrrr


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Why Sickle Cell Anemia socommon in people of Africaand Indian ancestry? Malaria kills on average 1.2 million people

Malaria is most prevalent in the southern hemisphere,particularly in Africa and Southern Asia


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Why Sickle Cell Anemia socommon in people of Africaand Indian ancestry?

Malaria is caused by the bite ofinfected Anopheles mosquitoes.

Infected mosquitoes carry a parasiticprotozoan ( microorganism)

The parasite spends the first stage of its life

cycle in the salivary glands of themosquito Anopheles Gambiae.


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Why Sickle Cell Anemiaso common in people of

Africa and Indianancestry? When an infected mosquito bites a human, the

malaria parasite enters the red blood cells. The parasites multiply inside the red bloodcells.

After 48 to 72 hours, the infected red blood

cells burst, infecting more red blood cells. The parasite spreads throughout the body andeventually infects the liver.


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People who inherited one copy of the sickle cellallele had red blood cell membranes that did notadmit the parasite.

Carriers had more children and passed theprotective allele to approximately half of them.

Why Sickle Cell Anemia so

common in people of Africaand Indian ancestry?


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Why Sickle Cell Anemia socommon in people of

Africa and Indianancestry?

Due to Malaria being prevalent in Africa and India,

the frequency of sickle cell allele increased from0.1% to over 45% over 35 generations.

This is because carriers for the sickle cell allelehave some natural protection against malaria.


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The sickle cell gene provides 60% protection

against overall mortality of Malaria

This is why the frequencies of sickle cellcarriers are high in malaria-endemic areas.

Researchers believe that the sickle cell allelemight have been brought over to Africa fromIndia or that the mutation might have startedin East Africa.


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Conclusion

There are effects atthe genetic level

There are effectsat the proteinlevel

There areeffects at thecellular level

Negative effects at the organism level: symptoms

Positive effects at the organism level: resistance to

malaria


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Works Cited

http://bionews-tx.com/news/2013/05/08/texas-am-team-takes-on-malaria-

with-incredible-results/

http://www.cdc.gov/malaria/about/biology/sickle_cell.html

http://

www.pbs.org/wgbh/evolution/educators/course/session7/explain_b_po

p1.html

http://www.mayoclinic.org/diseases-conditions/sickle-cell-anemia/basic

s/treatment/con-20019348

http://www.nhlbi.nih.gov/health/health-topics/topics/sca/signs.html

www.evolution.berkeley.edu/evolibrary/article/mutations_06

http://www.nhlbi.nih.gov/health/health-topics/topics/sca

Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, andAllied Health, Seventh Edition. 2003 by Saunders, an imprint of Elsevier,

Inc
http://bionews-tx.com/news/2013/05/08/texas-am-team-takes-on-malaria-with-incredible-results/http://bionews-tx.com/news/2013/05/08/texas-am-team-takes-on-malaria-with-incredible-results/http://bionews-tx.com/news/2013/05/08/texas-am-team-takes-on-malaria-with-incredible-results/http://www.cdc.gov/malaria/about/biology/sickle_cell.htmlhttp://www.pbs.org/wgbh/evolution/educators/course/session7/explain_b_pop1.htmlhttp://www.pbs.org/wgbh/evolution/educators/course/session7/explain_b_pop1.htmlhttp://www.pbs.org/wgbh/evolution/educators/course/session7/explain_b_pop1.htmlhttp://www.mayoclinic.org/diseases-conditions/sickle-cell-anemia/basics/treatment/con-20019348http://www.mayoclinic.org/diseases-conditions/sickle-cell-anemia/basics/treatment/con-20019348http://www.nhlbi.nih.gov/health/health-topics/topics/sca/signs.htmlhttp://www.evolution.berkeley.edu/evolibrary/article/mutations_06http://www.evolution.berkeley.edu/evolibrary/article/mutations_06http://www.nhlbi.nih.gov/health/health-topics/topics/scahttp://www.nhlbi.nih.gov/health/health-topics/topics/scahttp://www.nhlbi.nih.gov/health/health-topics/topics/scahttp://www.nhlbi.nih.gov/health/health-topics/topics/scahttp://www.nhlbi.nih.gov/health/health-topics/topics/scahttp://www.evolution.berkeley.edu/evolibrary/article/mutations_06http://www.nhlbi.nih.gov/health/health-topics/topics/sca/signs.htmlhttp://www.mayoclinic.org/diseases-conditions/sickle-cell-anemia/basics/treatment/con-20019348http://www.mayoclinic.org/diseases-conditions/sickle-cell-anemia/basics/treatment/con-20019348http://www.pbs.org/wgbh/evolution/educators/course/session7/explain_b_pop1.htmlhttp://www.pbs.org/wgbh/evolution/educators/course/session7/explain_b_pop1.htmlhttp://www.pbs.org/wgbh/evolution/educators/course/session7/explain_b_pop1.htmlhttp://www.pbs.org/wgbh/evolution/educators/course/session7/explain_b_pop1.htmlhttp://www.cdc.gov/malaria/about/biology/sickle_cell.htmlhttp://www.cdc.gov/malaria/about/biology/sickle_cell.htmlhttp://bionews-tx.com/news/2013/05/08/texas-am-team-takes-on-malaria-with-incredible-results/http://bionews-tx.com/news/2013/05/08/texas-am-team-takes-on-malaria-with-incredible-results/http://bionews-tx.com/news/2013/05/08/texas-am-team-takes-on-malaria-with-incredible-results/


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Exam uestions

List two differences between normal red

blood cells and sickle cells.

What is the probability of an offspring

having sickle cell disease (affected) ifboth parents are carriers?


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Exam uestions

How does being a carrier for the sickle cellallele protect you from malaria?

What protein, present in red blood cells, isin charge of carrying oxygen fromrespiratory organs to the rest of the body?

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Sickle Cell Disease -