Genetics Northern California

Inheritance Patterns

Genes are the inherited instructions your body uses for growth and healthy development. Humans have over 20,000 different genes. 

Most genes come in pairs. A child receives one copy of each gene from the egg and one copy from the sperm.  Genetic conditions are caused by variants (genetic changes or mutations) that affect the way a gene works. Variants may be inherited from your parents or happen as a brand new change. 

There are different ways a genetic condition can be inherited. The most common inheritance patterns are autosomal dominant, autosomal recessive, X-linked dominant, X-linked recessive, multifactorial, and mitochondrial inheritance.

Autosomal inheritance
"Autosomal" refers to traits determined by the genes located on the autosomes. The autosomes include all of the chromosomes except for the sex chromosomes. Humans typically have 22 pairs of autosomes and 1 pair of sex chromosomes for a total of 46 chromosomes. This means individuals typically have two copies of each autosomal gene, regardless of their sex. 
   Autosomal Dominant
   Autosomal Recessive

X-linked inheritance
"X-linked" refers to traits determined by genes located on the X chromosome and not the other 22 pairs of chromosomes (called autosomes). Most women have two X chromosomes and most men have one X chromosome and one Y chromosome. Inheritance of an X-linked condition is connected to the biological sex of a person.   
   X-Linked Dominant
   X-linked Recessive

Multifactorial inheritance
Multifactorial inheritance involves the interaction of genes from both sides of the family, as well as the influence of environmental factors.
   Multifactorial inheritance

Mitochondrial inheritance
Mitochondrial inheritance involves genes located in a part of the cell called the mitochondria. Mitochondria are located in egg cells, but not in sperm cells. So mitochondrial genes are only passed on through the egg.      
   Mitochondrial Inheritance

Inheritance patterns can sometimes be confusing. And it isn't always easy to know how a specific condition is inherited. Some genetic conditions can be inherited in more than one way.  If you have questions about a specific condition in your family and the possible type of inheritance, please call the nearest Genetics Department for a confidential consultation.

Last reviewed: March 2022

Reviewed by: Kimberly Barr, MS, LCGC