What are the chances my child will inherit a condition?
How Does Someone Get a Genetic Condition?
Many conditions are caused by one or more genes that do not work correctly in the body. Changes in a gene can cause it not to work or make it work improperly. These changes can be passed down from parents to children. So, if a parent has a gene that does not work properly, there is a chance that they can pass it down to their child.
If you or a family member has been told you have a genetic condition, often the first question you ask is, “Will my children have it, too?” This goes for any condition that comes from your genes—not just disease but eye or hair color, for example. The answer is: it depends.
Every child gets a mix of genes from mother and father, and that child’s parents got a mix of genes as well. Genes are collected into groups called chromosomes, and chromosomes come in pairs. In a simple sense, a parent gives a child one chromosome for each pair, and those pairs work together to make your body look and work the way it does. Because of this pairing, sometimes a nonworking gene won’t cause problems—the other member of the pair may be able to do the work by itself.
Whether your child will have a genetic condition depends on two main things:
- What is the chance (or probability) your child will receive the gene change—mutation—that causes the condition?
- Is one gene enough to cause the disease, or can your child also get a working gene that can help out?
We can’t always test everyone’s genes to see where the mutations are, and sometimes brand new mutations show up in a family, affecting only one person. But conditions can seem to “skip a generation,” too, and that’s where a family health portrait comes in.
Figuring Out the Chances
A family health portrait can help show a pattern in a family. That pattern helps healthcare providers and genetic counselors understand how a gene moves from parent to child. That way, they can get a sense of where a gene is in different people, even in the people who don’t have the condition caused by that gene.
When we speak of the chance of inheritance of a gene or condition, we often use terms like “50%” or “1 in 2.” These numbers are a bit like tossing a coin. If you toss a coin, there is a 50% (or 1 in 2) chance that it will come up heads, and 50% that it will come up tails. If it does come up heads, and you toss it again, there is still a 50% chance of getting heads. The first toss doesn’t change the chance of getting heads a second time. In fact, you could toss a coin 10 times in a row and get heads every time. It’s very rare, but it can happen.
The same rules of chance hold in genetic conditions. Having one child with a condition doesn’t mean that having another child with the same condition is any more or less likely. The chance is the same for each pregnancy. It is based only on what genes the parents can pass on. A geneticist or genetic counselor can help you calculate your child’s chances of inheriting different conditions.
It is also important to keep in mind that having nonworking genes does not guarantee that a person will develop signs and symptoms of a particular condition. Some people can have very severe symptoms, while some people remain relatively healthy. This varies from person to person and based on the condition. A geneticist or genetic counselor can help you determine the risk of developing signs and symptoms for a given condition.
Can We Always Know What the Chances Are?
Many disorders are caused by a combination of effects, such as multiple genes or the interaction between genes and the environment. The inheritance patterns for these conditions are more difficult to describe and are often unclear, even with a good family health portrait. Examples of these conditions include heart disease, schizophrenia, and certain types of cancer. Disorders caused by changes in the number or structure of chromosomes also do not follow the straightforward models of inheritance described above.
The Paths Genes Take
If you want to learn how genes move through a family and whether they show up or seem to skip a generation, see Main Inheritance Patterns.