Our genes serve as an operating manual for cells of the body. Genes tell cells what to do and when. But copying errors in those operating manuals — known as mutations — can lead to misspelled instructions that can change how cells operate. Scientists now know that some of those mutations can lead to disease. Others offer benefits. Some can do both. And the mutation that underlies sickle cell disease is one that can be both good and very bad.
In red blood cell that transport oxygen to tissues throughout the body. It wasn’t until 1949 that scientists learned altered hemoglobin causes red blood cells to take the shape of crescent moons. In fact, this condition was the first known example of a disease linked to inherited changes in a molecule.
Hemoglobin normally allows “red blood cells to be very floppy and pliable, and slip and slide through the blood vessels easily,” says Erica She’s a pediatrician at Boston Children’s Hospital and Harvard Medical School. Both are in Boston, Mass.
But a mutation in a single hemoglobin-making gene — the HBB gene — underlies sickle cell disease. This mutation makes hemoglobin stack in long strings inside blood cells. It gives those cells an inflexible, sickle — or crescent-moon — shape. Instead of being “squishy,” the now-stiff red blood cells get stuck inside blood vessels. This can cause severe and debilitating pain. Worse still, the sickle cells can literally block blood flow and the movement of oxygen into nearby tissues.
Sickle cell affects millions of people around the world. In the United States, for instance, about 100,000 people live with the disease. Most of them are Black or Latino. The mutation behind it is particularly common in people whose ancestors came from parts of Africa that are south of the Sahara, from parts of the Middle East or from Southeast Asia. Why? It turns out that these areas have high rates of malaria.
A bone marrow transplant is currently the only cure for sickle cell disease. A new can make sickle red blood cells. But such transplants are costly. Finding a matched donor to contribute marrow challenging, notes. That’s one reason researchers have begun looking to replace the mutant HBB genes. This part of one research team that is currently trying to fight the disease through such gene therapy.
A predecessor. It could be a family forebear, such as a parent, grandparent or great-great-great grandparent.
A tubular structure that carries blood through the tissues and organs.
The smallest structural and functional unit of an organism. Too small to see with the unaided eye, it consists of a watery fluid surrounded by a membrane or wall. Depending on their size, animals are made of anywhere from thousands to trillions of cells.
To emerge or to make come into being, either naturally or through human intervention, such as by manufacturing. (in biology) To grow as an organism from conception through adulthood, often undergoing changes in chemistry, size, mental maturity or sometimes even shape.
A condition where the body does not work appropriately, leading to what might be viewed as an illness. This term can sometimes be used interchangeably with disease.
A segment of DNA that codes, or holds instructions, for a cell’s production of a protein. Offspring inherit genes from their parents. Genes influence how an organism looks and behaves.
A molecule that binds to oxygen in the blood, carrying it around to tissues.
A term that the phrase that it modifies is precisely true. For instance, to say: "It's so cold that I'm literally dying," means that this person actually expects to soon be dead, the result of getting too cold.
A disease caused by a parasite that invades the red blood cells. The parasite is transmitted by mosquitoes, largely in tropical and subtropical regions.
Spongy tissue that develops inside of bones. Most red blood cells, infection-fighting white blood cells and blood platelets form within the marrow.
An electrically neutral group of atoms that represents the smallest possible amount of a chemical compound. Molecules can be made of single types of atoms or of different types. For example, the oxygen in the air is made of two oxygen atoms (O2), but water is made of two hydrogen atoms and one oxygen atom (H2O).
That describes some altered gene in an organism’s DNA. Such changes, known as mutations, may occur naturally. Others may be triggered by outside factors, such as pollution, radiation, medicines or something in the diet.
Various parts of an organism that perform one or more particular functions. For instance, an ovary is an organ that makes eggs, the brain is an organ that makes sense of nerve signals and a plant’s roots are organs that take in nutrients and moisture.
A gas that makes up about 21 percent of Earth's atmosphere. All animals and many microorganisms need oxygen to fuel their growth (and metabolism).
An organism that gets benefits from another species, called a host, but doesn’t provide that host any benefits. Classic examples of parasites include ticks, fleas and tapeworms.
Who works in the field of medicine that has to do with children and especially child health.
Compound made from one or more long chains of amino acids. Proteins are an essential part of all living organisms. They form the basis of living cells, muscle and tissues; they also do the work inside of cells. Among the better-known, stand-alone proteins are the hemoglobin (in blood) and the antibodies (also in blood) that attempt to fight infections. Medicines frequently work by latching onto proteins.
Colored red by hemoglobin, these cells move oxygen from the lungs to all tissues of the body. Red blood cells are too small to be seen by the unaided eye.
A condition where blood stops flowing to part of the brain or leaks in the brain.
Treatment intended to relieve or heal a disorder.
The replacement of organs, tissues or cells with those from another organism. It is also a term for the material that will be moved.
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