Sickle Cell Inheritance

Exploring Genetics and Probability

What is sickle cell?

• Sickle cell is a genetic condition that causes the red protein in blood (hemoglobin) to make the blood cells rigid and pointy.

• The gene for sickle trait is spread throughout the world.

• It was most common in the areas where there was a lot of malaria because sickle trait actually helps people survive malaria.

What is sickle trait?

• In order to inherit anything from your parents, you get one gene from each parent.

• The way sickle cell disease occurs is if you get a sickle gene from both your parents.

• If you only get one sickle gene and your other gene is normal, you have sickle trait.

Health Benefit of Sickle Trait

• Protects against risk of death from malaria infection.– Malaria kills thousands of kids a year.

• Note: only sickle trait gives protection against the deadly strains of malaria

More on Malaria

• Caused by a parasite that can live in mosquitoes

• Parasites infect red blood cells• Symptoms include fever, vomiting, headache• Can cut off blood supply to vital organs• Different strains of malaria, some are deadly• Children are very susceptible to dying of

malaria

Myth vs Reality

• Myth: Only African Americans get sickle cell.• Reality: Sickle cell affects people of all

different racial and ethnic backgrounds.– African, Arabian, Israeli, Turkish, Pakistani– Greek, Hispanic, Italian– Blond hair/blue eyed children of Northern Europe– One case in Hong Kong!

Where do people have sickle cell?

• Highest frequency in Sub-Saharan Africa• Also prevalent across the US, on the Atlantic

side of Central and South America, the Caribbean, Europe, North and Central Africa, the Middle East and South Asia.

Map from Dr. Lewis Hsu, MD, PhD, Professor of Pediatrics, Director of Pediatric Sickle Cell, University of Illinois, Chicago, IL

Inheriting a sickle gene

This is a genetic condition, so whether somebody gets sickle cell disease or sickle trait depends completely on what genes you get from your parents.

The Inheritance Game

A S – Sickle traitS S – Sickle Cell DiseaseA A – Normal

Modeling inheritance

A A Normal

A S Sickle trait

A S Sickle trait

S S Sickle cell disease

A S Sickle trait

A

SSickle trait

Mother’s genes

Father’s genes

Acknowledgements

• Adapted from ideas by – Camille Coleman, Genetic Counselor, Marian

Anderson Comprehensive Sickle Cell Center, St. Christopher’s Hospital for Children, Philadelphia, PA

– Lewis Hsu, MD, PhD, Professor of Pediatrics, Director of Pediatric Sickle Cell, University of Illinois, Chicago, IL

– Rebecca Hui, 4th Grade Teacher, St. Frances of Rome School, Chicago, IL

References and Related Resources

• Center for Disease Control• Sickle Cell Information Center