SICKLE-CELL ANEMIA

PRESENTED BY: LUKES GUTIERREZ

WHAT IS SICKLE CELL ANEMIA

• Most common form of Sickle Cell Disease (SCD)• Hereditary blood disorder – abnormality in

hemoglobin molecule in red blood cells• Hemoglobin transports oxygen from respiratory

organs to the rest of the body.• Normal hemoglobin (hemoglobin A) replaced by

sickle hemoglobin (hemoglobin S).

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)

INCIDENCE

• Most commonly inherited blood disorder in the US

• Over 2 million Americans are carriers of SCD• 70,000-80,000 affected Americans• Highest incidence rate in African- Americans

when compared to other ethnicities. • 1 out of 350 are affected• 1 in 12 are carriers

INCIDENCE

• NOT only people of African ancestry but also of Mediterranean, Middle Eastern, Indian ancestry, and people from the Caribbean and parts of Central and South America.

• 1 out of 36,000 Hispanic-American births are affected and 1 in 100 are carriers.

SYMPTOMS • Present at birth • Most common are anemia and pain • Hand-foot syndrome• Frequent infections• Delayed Growth • Vision Problems• Symptoms can vary per person

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

TREATMENT

• No widely available cure• Bone marrow transplant (only

potential cure)• Aimed at avoiding crises,

relieving symptoms and preventing complications

• Medications to reduce pain are available

• Blood transfusions and supplemental oxygen

TESTING • Blood Test can check for hemoglobin S• If negative—no sickle cell gene present• If positive—further tests are done to determine

if there are one or two sickle genes present • Can be done before birth through sampling

fluid surrounding the unborn baby in the womb

• With good health care, many people who have sickle cell anemia can live productive lives and today are living into their forties and fifties

GENE• Mutation on hemoglobin-Beta gene.• The allele responsible is in the short arm of chromosome 11.• 6th amino acid (glutamic acid) replaced by valine and changes the

function.• Known mutation of a single nucleotide (A to T).• CTC codon CAC codon which is transcribed from the template

strand into a GUG codon.

INHERITANCE PATTERN

• Autosomal recessive pattern of inheritance.• In carriers (heterozygous Rr) problems are minor

– normal allele produces over 50% of the hemoglobin.

• Symptoms only if deprived oxygen.

Retrieved from the National Heart, Lung and Blood Institute website

Rr

Rr Rr

Rr Rr

RrRr RrRr RrRr

Rr Rr

Rrrr

rr rr

rrrrrrrrRR

RR RR

RR

RR rr

rr

rrrr

WHY SICKLE CELL ANEMIA SO COMMON IN PEOPLE OF AFRICA AND INDIAN ANCESTRY?

• Malaria kills on average 1.2 million people• Malaria is most prevalent in the southern hemisphere,

particularly in Africa and Southern Asia

WHY SICKLE CELL ANEMIA SO COMMON IN PEOPLE OF AFRICAAND INDIAN ANCESTRY?

• Malaria is caused by the bite of infected Anopheles mosquitoes.

• Infected mosquitoes carry a parasitic protozoan ( microorganism)

• The parasite spends the first stage of its life cycle in the salivary glands of the mosquito Anopheles Gambiae.

WHY SICKLE CELL ANEMIA SO COMMON IN PEOPLE OF AFRICA AND INDIAN ANCESTRY?

• When an infected mosquito bites a human, the malaria parasite enters the red blood cells.

• The parasites multiply inside the red blood cells.• After 48 to 72 hours, the infected red blood cells

burst, infecting more red blood cells.• The parasite spreads throughout the body and

eventually infects the liver.

WHY SICKLE CELL ANEMIA SO COMMON IN PEOPLE OF AFRICA AND INDIAN ANCESTRY?

• People who inherited one copy of the sickle cell allele had red blood cell membranes that did not admit the parasite.

• Carriers had more children and passed the protective allele to approximately half of them.

WHY SICKLE CELL ANEMIA SO COMMON IN PEOPLE OF AFRICA AND INDIAN ANCESTRY?

• Due to Malaria being prevalent in Africa and India, the frequency of sickle cell allele increased from 0.1% to over 45% over 35 generations.

• This is because carriers for the sickle cell allele have some natural protection against malaria.

• The sickle cell gene provides 60% protection against overall mortality of Malaria

• This is why the frequencies of sickle cell carriers are high in malaria-endemic areas.

• Researchers believe that the sickle cell allele might have been brought over to Africa from India or that the mutation might have started in East Africa.

CONCLUSION• There are effects at

the genetic level There are effects

at the protein level

There are effects at the cellular level

Negative effects at the organism level: symptoms Positive effects at the organism level: resistance to

malaria

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_pop1.html

• http://www.mayoclinic.org/diseases-conditions/sickle-cell-anemia/basics/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, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc

EXAM QUESTIONS

• List two differences between normal red blood cells and sickle cells.

• What is the probability of an offspring having sickle cell disease (affected) if both parents are carriers?

EXAM QUESTIONS

• How does being a carrier for the sickle cell allele protect you from malaria?

• What protein, present in red blood cells, is in charge of carrying oxygen from respiratory organs to the rest of the body?