Find answers to frequently asked questions about genetic disorders, genetic testing, newborn screening, and more. Click on each question to reveal the answer.
What is DNA?
DNA stands for deoxyribonucleic acid. DNA is a long thread, or strand, of the four building blocks of life, called nucleotides. There are four types of nucleotides, called A, T, C, and G. These nucleotides are combined in different orders to create strands of DNA. The strands of DNA in our bodies are coiled up tight into packages we call chromosomes. And just like words are made up of letters that we can read in a book and understand, the body can read the nucleotides along the DNA and understand what they mean. Some of the combinations of nucleotides in our DNA make our genes.
DNA contains the instruction manual for our bodies. It is our genetic code that tells our body how to grow, develop, and function. It can be helpful to think of DNA as a book that contains all the information needed for a human to exist. In the human body, DNA is found in the nucleus (center) of every cell in our body.
What is a chromosome?
Chromosomes are structures made up of DNA. Going back to the analogy used for DNA, chromosomes would be chapters within your book.
Humans have 46 total chromosomes that come in 23 pairs. One chromosome in each pair is inherited from each parent. The first 22 pairs, called autosomes, are expected to be the same for every person. The last pair is called the sex chromosomes. There are two of these, called the X chromosome and the Y chromosome. Typically, females have two X chromosomes and males have one X chromosome and one Y chromosome.
Sometimes a person inherits too many or too few chromosomes or has a structural change to a chromosome (such as a missing or extra piece). This is called a chromosomal abnormality and may cause a disorder. These changes affect a large amount of DNA and can affect a large number of genes.
What is a gene?
A gene is a small piece of DNA. A large number of genes are located in the DNA on each chromosome. Many of our genes tell the body how to make different proteins. Proteins carry out specific jobs in the body and make our bodies work. Using our book analogy, a gene is a sentence within a chapter of our book. Genes help determine how our body develops and functions, such as the color of our hair, our height, and the speed of our metabolism.
What is a mutation (variant)?
A mutation, also called a variant, is a change within DNA. Not all of these changes cause a problem. A benign variant is one where the change does not cause a problem. Another type of mutation is called a pathogenic variant. Pathogenic variants prevent the gene from functioning the way it should. This type of variant can cause a disease or disorder. There are other variants that can change a gene in a way where we don’t have enough information to know if it will cause a problem or not. These are called variants of unknown significance (VUS).
What is a somatic mutation?
A somatic mutation is a change in the DNA that is not present in all cells of the body. One example would be a genetic change found within a tumor that isn’t found in the person’s other cells in the rest of the body. Somatic mutations cannot typically be passed from a parent to a child.
What is a germline mutation?
A germline mutation is a change that starts in the germ cells, also known as the sperm or egg cells. When someone has a genetic diagnosis caused by a germline mutation, this means they have this mutation in all of their body’s cells. Germline mutations can be passed from a parent to a child. There are different ways that germline mutations can be inherited: autosomal dominant, autosomal recessive, X-linked dominant, X-linked recessive, Y-linked, co-dominant, and mitochondrial. Learn more →
Where can I find out more about genes and genetics?
The Centers for Disease Control and Prevention (CDC) provides some basic information about genes and genetics.
What is a genetic condition?
Genetic conditions are medical conditions that are caused by changes in our genes or chromosomes. Some conditions can run in families, such as cystic fibrosis, sickle cell anaemia, Huntington disease, and BRCA-associated cancers. Other genetic conditions such as Down syndrome do not typically run in families.
Where can I find out more about my genetic condition?
Your genetics team members will provide information about your condition when you attend your genetics clinic appointment. They may also be able to put you in touch with local and national support groups.There are several well-trusted websites that provide information about various genetic conditions.
Some genetic conditions are tested for in newborns. Websites that include information about these tests and conditions include:
Other sources of information about genetic conditions include:
- Think Genetic
- National Organization for Rare Disorders
- Genetic and Rare Diseases Information Center:
Your genetics team may also be able to direct you to other trusted websites for information.
Why do people attend a genetics clinic?
People attend a genetics clinic to find out if they or someone in their family has a genetic disorder and, if so, what that means for them. Some of the reasons why you might have been referred to clinical genetics include:
- You have a known genetic condition in the family and want to know the risks to you and/or your children.
- You have a child with difficulties that may be due to a genetic condition and want to see if a diagnosis can be made.
- You have a strong family history of cancer and want to know if you are at increased risk, and, if so, what options are available to you.
- You have a known genetic condition and want specialist advice about the condition.
- You or your partner are pregnant and have a possible genetic condition in the family. You want to know if a diagnosis can be made and, if so, your risks and options.
- You or your partner have been told that a test during pregnancy has given an abnormal result and want to talk about what the result means and what options are available.
- You or your partner have experienced two or more pregnancy losses (miscarriages), a stillbirth, or a baby who died, and you want to find out there is a genetic reason for your loss.
How can I get referred to a genetics clinic?
People are usually referred to a genetics clinic by their primary doctor. Pregnant women may also be referred by their obstetricians. If you believe that you would benefit from a referral to a genetics clinic, talk to your doctor or other health care provider.
How can I prepare for a genetics appointment?
Make a list of specific questions that you have for the genetics team so that you don’t forget to ask any of them.
Before your appointment, ask your family about their health history. We will ask for health information about your children, brothers, sisters, parents, aunts, uncles, nieces, nephews, cousins, and grandparents. It can be helpful to write this information down before your appointment and bring a copy of it with you.
You should collect the following information:
- Who in your family has similar symptoms to you (or you child) and about how old they were when those symptoms started.
- Who in your family has been diagnosed with any genetic condition, the name of the condition, and about how old your relative was when they were diagnosed.
- Approximate ages of your living relatives.
- Ages at which relatives died and cause of death.
- Your ancestry on both sides of the family (for example: English, African-American, Jewish).
It is also important to ask your relatives if they have had any related genetic testing. With their permission, please bring a copy of their results with you to your appointment.
What happens at a genetics clinic appointment?
Your genetics team will provide information, offer support, and address your specific questions and concerns. To determine whether your problem is due to a genetic disorder, the genetics team will ask about your (or your child’s) symptoms and take a detailed family history. The genetics team may also perform a physical exam and recommend appropriate tests.
If a person is diagnosed with a genetic disorder, the genetics team will provide information about the diagnosis, how the condition is inherited, the chance of passing the condition to future generations, and the options for testing and treatment.
The details about what happens at a genetic clinic appointment will depend on your unique circumstances, but typically include:
- A discussion of the problem that has brought you to the clinic.
- A discussion of your family. A family tree will be drawn, and medical details of relatives may be asked about (such as the cause and age of their death). It is useful to have found out these details before you come to the clinic.
- A medical exam of the patient and other family members who may also have the problem.
- A discussion of what the doctor finds, and what your options are.
- Answering your questions.
- Providing help in understanding your options and making your own decisions.
- Tests (such as blood tests) may be offered. Some tests are available on the same day, but often you will be asked to take some time to make a decision and come back another day.
- Making a plan for further information gathering (by you or the doctor), special tests, or another appointment.
- A letter will be sent to you afterward, going over what was discussed in the appointment and who to contact if you still have questions or if anything is unclear.
What does a genetic test involve?
Genetic testing, sometimes also called genomic testing, finds changes in genes or chromosomes that can cause health problems. A genetic test is usually done using a sample of blood or saliva. The sample is sent to a genetic testing laboratory to be analyzed. You will be told when to expect the results of your test. Depending on the reason for your test, it could take weeks or months. You may need further tests.
What is genetic counseling?
Genetic counseling gives you information about genetic conditions in your family. Your genetic counselor may ask you questions about your condition and about your family history, and will calculate the chance that you or someone else in your family will have the condition. They can also advise you about genetic testing for you and other family members, and help you and your family decide what is best for you. Genetic counselors also help you to understand the results of genetic tests.
Are my relatives at risk of having the same genetic condition?
Some, but not all, genetic conditions can run in families. The chance of a relative having the condition depends on the specific condition. Not all genetic conditions are passed on in the same way. The genetics team will discuss with you how the genetic condition in your family is passed on, and what it means for your family.
Should my children be tested for a genetic condition that is in the family?
Some genetic conditions can affect children’s health. In these cases, your genetics team may discuss the option of genetic testing in a child. However, many genetic conditions do not affect a child’s health. Rather, they only affect people when they are adults. In these cases, testing is not appropriate for children. When the child is older, they can consult a genetics specialist and decide for themselves whether or not they want to pursue genetic testing.