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What is DNA?

Our bodies are made up of trillions of tiny pieces called cells.  These cells contain a special substance called DNA.  DNA is the blueprint that tells that our cells what do to.  A specific piece of this DNA is called a gene.  Some people carry genetic changes in their genes.  These mutations are sometimes called variants or mutations.  If your DNA is an instruction manual for your cells, then a genetic change can be considered a “spelling error”.

Spelling errors in genes can sometimes lead to health problems.  Some genetic changes place us at a slightly increased risk for a health problem, but other genetic changes can cause major health problems. 

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What is Genetic Testing?

Genetic testing is the process of analyzing your DNA for these spelling errors.  If you or a family member undergo genetic testing, it is important to know the potential results.

1. Positive – A genetic change was identified that the lab believes can cause a health problem.  The laboratory report will frequently label these changes as, “pathogenic” or “likely pathogenic”.

2. Negative – The lab did not find any genetic changes.  It is important to know that scientists are always making new gene discoveries.  A negative result does not guarantee that you don’t have a genetic disease, but simply means that they didn’t identify anything in the parts of the DNA they were looking.

3. Uncertain – Genetic testing frequently identifies genetic changes the lab has never seen before.  The labs typically call these, “variants of uncertain significance” or “VUS” for short.  Everyone is unique and that is because we carry genetic changes that make us one-of-a-kind.  These VUSs may just be one of those genetic changes that make someone unique.  Alternatively, they may be a genetic change that causes health problems.  Your doctor will help investigate a VUS and tell you if they think it can cause health problems or not.

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How are Genetic Changes Inherited?

X-linked, autosomal recessive, and autosomal dominant inheritance are ways genes pass from parents to children. Each has its own rules:

1. X-Linked Inheritance:

   • Some genes live on the X chromosome, one of the sex chromosomes. Girls have two X's (XX), and boys have one X and one Y (XY).

   • If a gene on the X chromosome is broken, it can cause a problem. Boys are more affected because they have only one X. Girls can either be affected or unaffected depending on the specific disorder. Unaffected girls are typically called carriers.  They can give the broken gene to their kids.

   • A female can pass the broken gene to her children.  There is a 50% chance to pass the condition to each of her children.  A male can also pass the broken gene to his children.  There is <1% to pass the condition to a male child and a nearly 100% chance of passing the condition to a daughter. 

2. Autosomal Recessive Inheritance:

   • To have a problem with these genes, you need two broken copies, one from each parent. If you have one broken and one normal copy, you're a carrier but not affected.

   • If two parents have a child with an autosomal recessive condition, they usually have a 25% chance of having another child with the same condition.  Once someone is born with an autosomal recessive condition, they are unlikely to pass the condition on to their children, but their reproductive partner should still be offered genetic testing. 

3. Autosomal Dominant Inheritance:

   • To have a problem with these genes, one broken copy is enough for the problem to show up.

   • If a parent has a broken gene, there's a 50% chance their kids will get it too. Sometimes these genes show up in every generation.  Sometimes these broken genes are brand new in an individual, we typically call these de novo mutations.  De novo mutations are not typically inherited from a parent, but once someone has one, their future children are at risk of inheriting the same mutation. 

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