Autosomal Dominant & Autosomal Recessive

What are inherited traits?

Humans receive traits from their parents, like your eye and hair color or how tall you are. Inheritance is the process of how you receive your traits.

What is autosomal dominant inheritance?

Autosomal dominant is one way that genetic traits pass from one parent to their child. When a trait is autosomal dominant, only one parent needs to have an altered gene to pass it on. Half of the children of a parent with an autosomal trait will get that trait. Only changes that occur in the DNA of the sperm or egg can be passed on to children from their parents.

What is autosomal recessive inheritance?

Autosomal recessive is a pattern of inheritance. If a parent has an autosomal recessive trait, they'll show no symptoms. In order to pass it on to their children, both parents need to carry the trait. But because they don’t have any symptoms, they often don’t even know they have it. Both parents need to pass an altered gene onto their child for their child to inherit the genetic condition or trait in an autosomal recessive pattern. One quarter of children will get an autosomal recessive gene if both parents have it. Only changes that occur in the DNA of the sperm or egg can be passed on to children from their parents.

What does autosomal mean?

Autosomal means that a specific gene is not on a sex chromosome and is a numbered chromosome. Humans have 46 total chromosomes. Each of your parents gives you 23 chromosomes via the egg or sperm, for a total of 46. There are two sex chromosomes (X and Y) and 22 numbered chromosomes. The numbered chromosomes are the only chromosomes that use autosomal inheritance patterns.

How do I inherit traits?

Traits are passed from the sperm and egg. Genetic material consists of:

• DNA.
• Genes.
• Chromosomes.

Chromosomes are made up of DNA, and chunks of that DNA form genes. That DNA holds your genetic code. You receive one copy of a gene from each parent, creating a pair. Those genes are in your cells, which divide and copy themselves until your body has enough cells to make up all of your body. When the cells divide, the chromosomes and genes should stay the same in each cell of the same line. Sometimes during division there's a mistake in the division of genetic material. That's called a mutation. It may change the function of the cell it's in.

How do inherited traits affect my body?

Inherited traits determine your physical characteristics, including how you look and what makes you unique.

Sometimes, you can inherit genes that have altered DNA (genetic mutation) that form as a result of a copying mistake during cell division. Mutations may lead to genetic conditions that affect how your cells form and function, but they don’t always. Some genes can mutate and not cause disease, and some can cause serious illness if they mutate.

Where is DNA in my body?

DNA lives in every cell in your body — generally in the nucleus, which is the control center of the cell. Trillions of cells make up who you are.

What does DNA look like?

Your DNA is made of four bases: adenine (A), cytosine (C), thymine (T) and guanine (G). The bases form pairs (base pairs): A with T and C with G. The base pairs connect with a sugar molecule and a phosphate molecule (forming a nucleotide) that create a spiral staircase (double helix). The base pairs form the steps and the sugar and phosphate molecules are the rails.

How does a mutation change my DNA?

A genetic mutation can happen during cell division or if the cell is exposed to something toxic. A mutation is a change in DNA’s double helix structure. This means that a gene isn't where it's supposed to be on a chromosome. Mutations can be caused by:

• Substitution: One nucleotide switches place with another nucleotide.
• Insertion: An extra nucleotide is added to a strand of DNA.
• Deletion: A nucleotide is removed from a strand of DNA.

What are common genetic disorders caused by autosomal dominant inheritance?

Genetic disorders that follow a pattern of autosomal dominant inheritance include:

• Huntington’s disease.
• Marfan syndrome.
• Achondroplasia.

What are common genetic disorders caused by autosomal recessive inheritance?

Genetic disorders that follow a pattern of autosomal recessive inheritance include:

• Cystic fibrosis.
• Sickle cell disease.
• Tay-Sachs disease.

Is there a test to check the health of my genes?

There are multiple ways to test for genetic problems. A genetic test identifies changes to your genes, chromosomes or proteins. Genetic testing can locate mutated genes that cause genetic conditions. These tests help parents who plan on having children understand their risk of passing a genetic condition to their child.

How do I prevent genetic disorders from passing to my children?

It's not possible to determine which genes to pass on to children, so it isn’t possible to prevent genetic conditions from passing to your children. To better understand your risk of passing a specific genetic condition that runs in your family, talk with your healthcare provider about genetic testing and speak with a genetic counselor who can walk you through the test results.

How do I keep my DNA healthy?

You can keep your DNA healthy by:

• Eating a well-balanced diet.
• Exercising.
• Not smoking.
• Reducing the amount of alcohol you drink.
• Staying up to date on wellness visits with your healthcare provider.

A note from Cleveland Clinic

Your parents give you the traits that make you unique. Genetic conditions are passed in a variety of different ways. If you plan on becoming pregnant and want to understand your risk of passing a specific gene or genetic condition to your child, talk with your healthcare provider about genetic testing or genetic counseling.