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Genetics and Inheritance of Sickle Cell
Sickle Cell

Sickle cell disease is caused by a specific alteration in one gene from both parents. Thus a person who is born with it, will have it for their whole life, making it a lifelong condition. Learning about the role that genes play can help you and your loved ones better understand what causes the disease and its symptoms.
“I did not understand sickle cell. I had less education about it...So being educated on what sickle cell is made it a lot easier for me to understand myself.”

— Aaron, Sickle Cell Survivor

Genetics 101:
Cells, Genes, Proteins, and Your Sickle Cell

Every living thing is made up of many building blocks called cells. The human body has trillions of cells, and they are divided into many different types: muscle cells, bone cells, red blood cells, and white blood cells.


Cells

All cells work together to keep us alive. They carry out functions like converting food to energy.  Inside the cells is DNA, which tells the cell what to do.

Genes are made of DNA. They are like an instruction manual for your body. Some genes have a very important job to do because they contain instructions that tell each cell to make proteins.


DNA


Proteins are the workers of the cell. They perform a number of different functions within our bodies to keep us healthy. Proteins are required for the structure, function, and regulation of our body’s tissues and organs. 



Protein
 

Image of cells Image of DNA Image of protein Image of organs in the body.  Certain organs can be affected by sickle cell disease.
Cells DNA Protein Organs/Body

Your body relies on cells, genes, and proteins to work together to function properly. Explore the sections below for a closer look. 


Organs/Body

To better understand how genes and proteins work together, it’s helpful to think of genes as coded instructions that decide what an organism is like. Your genes instruct proteins to influence the expression of a physical trait (like eye color). 

For example, proteins create an eye color that is unique to you (brown, hazel, grey, blue, etc.) based on the instructions from your genes. People inherit genes from their parents, which is why children often share physical traits (and other characteristics) with their mother and father. 

Genes usually come in pairs: one copy of a gene comes from your mother and one copy comes from your father. Think of a pair of genes written down as two letters.

In the diagram below (known as a punnett square), these genes are represented by the letters A and S. Each child receives a pair of letters (genes).

This set of letters (genes) is known as a genotype. This diagram can show the likelihood of a specific trait being passed down from parents onto children. For example, along the left side of the square are the two genotypes from the mother, and across the top are the two genotypes from the father. Inside the overall square are four smaller squares, each representing one of four possible combinations that could occur in children.

Sickle cell Punnett SquareSickle cell Punnett Square

A genotype determines how a characteristic you inherit will show up in you. Your genotype is unique to you, and your inherited characteristic may not show up the same way it does in other people.

Red blood cells play an important role in your body. They carry oxygen from the lungs to your organs and move carbon dioxide from your organs back to your lungs. This cycle allows oxygen to fuel your organs by giving them the energy they need to function.

Red blood cells rely on a protein within the cell to do the actual work of carrying the oxygen. This protein is called hemoglobin. Hemoglobin is made up of 4 smaller proteins: 2 beta (β)‑globin proteins and 2 alpha (α)‑globin proteins. There must be an equal balance of both healthy β‑globin and α‑globin in order for adult hemoglobin to work properly.

The instructions from the HBB gene create the β‑globin proteins. If there is a change (mutation) in the HBB gene, the instructions for β‑globin are incorrect and cause your body to produce an abnormal form of β‑globin called hemoglobin Sickle (HbS). There is more than one type of sickle cell, which depends on the type of mutation in the HBB gene. Common types include hemoglobin SS, hemoglobin SC, hemoglobin Sβ+ thalassemia, and hemoglobin Sβ0 thalassemia.

How is Sickle Cell Inherited?
It’s important to remember that sickle cell is an inherited disease. This means that it is not contagious, and you can't catch it from other people like you can catch a cold or the flu. People with sickle cell have the disease because they inherit two sickle cell genes, one from each parent. These genes cause the production of hemoglobin Sickle (HbS) instead of normal hemoglobin (HbA).

It’s important to remember that sickle cell is an inherited disease. This means that it is not contagious, and you can't catch it from other people like you can catch a cold or the flu. People with sickle cell have the disease because they inherit two sickle cell genes, one from each parent. These genes cause the production of hemoglobin Sickle (HbS) instead of normal hemoglobin (HbA).
Chart showing sickle cell inheritance pattern

Sickle Cell Trait

Parents can pass the HBB gene along to their children. So, if a person inherits 1 copy of this sickle HBB gene and 1 copy of a normal HBB gene, they carry the sickle cell trait. Although those who carry the trait may not have symptoms of sickle cell, they can experience some of the symptoms of sickle cell under extreme circumstances. Conditions such as high altitudes, severe dehydration and low oxygen can lead to kidney and spleen complications, and even sudden death with extreme exertion.

When both parents carry the sickle cell trait, there is a 1 in 4 chance in each pregnancy of having a child with sickle cell. A simple blood test from your doctor can determine if you are a carrier.

Photo of Shamonica, living with sickle cell disease
 

We need broader education so that people know if they have sickle cell trait.”

We need broader education so that people know if they have sickle cell trait.”

SHAMONICA

Living With Sickle Cell

What Can You Do?

Educating others in your community by sharing what you’ve learned about the role genes play in sickle cell can help spark change in the disease. Learn more about the history of sickle cell and how the Black Panther Party created a
bigger movement for change.
Every voice, no matter how big or small,
can spark a conversation and action to
help drive change for sickle cell.


Recognizing how sickle cell impacts your
life may help spark important
discussions with others.
How does sickle cell affect you?