What Are Recessive Genetic Disorders? Everything You Need to Know

What is a recessive genetic condition? We take a look at the facts you need to know, exploring the most common recessive genetic disorders and the importance of genetic carrier screening.

How are recessive genetic disorders passed on?

For the most part, genetic disorders fall into two categories in terms of inheritance patterns: dominant and recessive.

We inherit two copies of each of our genes: one from our father and one from our mother. Genetic diseases are caused by gene abnormalities, defined scientifically as a change that renders the gene different from that found in a normal, healthy person.

In the case of a dominant genetic disorder, a person need inherit only one faulty gene copy in order to be born with the disorder.

In recessive genetic disorders, both parents must carry the same gene mutation in order for their child to be born with the disorder. If a person inherits just one copy of a gene mutation, he or she will not have that disorder, but will instead be a carrier.

How can I carry a genetic disorder without showing any symptoms?

The survival instinct is, through thousands of years of evolution, genetically ingrained in every cell of the human body. Our bodies are incredibly resilient and resourceful.

Gene mutations are actually quite common. In the majority of cases, when the body detects a faulty gene copy, it will simply revert to the healthy copy, effectively ignoring the gene mutation. It is in this way that carriers of gene mutations are usually unaffected. However, they may pass that gene mutation on to their child who could be born with the condition.

If I carry a recessive disorder, what is the likelihood of passing it on to my children?

If one partner carries a recessive gene mutation but the other does not, as discussed, their child will not be born with the associated disorder, but could be a carrier.

If both parents carry the same recessive gene mutation, there is a 50 percent chance that their child will be born a carrier. There is a 25 percent risk that their child will be born with the disorder. There is also a 25 percent child that their child will be born neither a carrier nor with the condition.

What are some of the most common recessive genetic disorders?

Examples of recessive genetic diseases include sickle cell anemia, Tay-Sachs disease and cystic fibrosis.

Sickle cell anemia

This comparatively common genetic disorder is more prevalent in individuals of African origin, though it is found in all ethnicities. Sickle cell is a disorder of the red blood cells; it causes anemia.

Instead of being the normal, smooth, oval-shape, the red blood cells of someone who has this genetic disorder form characteristic sickle shapes. This hinders the ability of red blood cells to travel efficiently around the body, delivering vital oxygen to tissue and organs.

Sickle-shaped red blood cells can become trapped in blood vessels, where they can build up and cause painful blockages. Blockages can also lead to secondary complications, such as tissue and organ damage due to lack of oxygenation.

Tay-Sachs disease

Around 1 in 27 people of Ashkenazi Jewish lineage carry this disorder, though it is found in people of all ethnic origins. Tay-Sachs disease is a fatal childhood disorder. The absence of an important enzyme called hex A leads to the build up of a fatty substance around nerve cells in the brain in people with this recessive hereditary condition.

Tay-Sachs disease generally affects the developing fetus, with signs of disease becoming apparent within a year of birth. At this time, there is no cure for Tay-Sachs disease.

Cystic fibrosis

Cystic fibrosis is the most common genetic disease among Caucasians. This genetic disease causes the body to produce a thick sticky mucus that can build up in the lungs and digestive tract, causing infection and impairing function. Cystic fibrosis can affect the pancreas, reducing the body’s ability to absorb essential nutrients. It can also cause infertility.

Cystic fibrosis was considered a fatal childhood illness until relatively recently. Increased research and understanding of the hereditary illness have led to improved management and treatment. People with cystic fibrosis today can live functional lives well into adulthood — and beyond.

No one in my family is affected by a genetic disorder. Is carrier screening necessary?

Recessive gene mutations only reveal themselves when two carriers of the same gene mutation have a baby.

Nevertheless, because these gene mutations cause no symptoms in carriers, they can be passed down through generation after generation. This means that they may suddenly appear in families with no prior known links to genetic disease.

The American College of Obstetricians and Gynecologists recommends genetic carrier screening for any woman planning to have a child, irrespective of ethnicity or family history. Expanded carrier screening facilitates testing for over 100 genetic diseases from a single sample.

Health insurance companies cannot use the results of carrier screening in assessing policy premiums. Additionally, medical insurers often cover the cost of genetic carrier screening.