Genetics Northern California

Inheritance Patterns

Genes give the body the instructions it needs for growth and healthy development. Most genes come in pairs; a child receives one copy of each gene from the mother and one from the father. Everyone has some genes that have the potential to cause serious disease. Whether they do or not is beyond human control. There is nothing any parent can do to cause or prevent a change in a gene.

Genetic disorders are caused by changes in the genetic instructions; there are many different ways genetic disorders 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. Autosomal disorders generally affect both males and females in the same way. 
   Autosomal Dominant
   Autosomal Recessive

X-linked inheritance
"X-linked" refers to traits determined by genes located on the X chromosome only and not the other 22 pairs of chromosome known as autosomes. Women are born with two X chromosomes and men with one X chromosome and one Y chromosome. depends specifically on the sex of the individual. 
   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 maternal egg cells, and not in sperm cells, so these genes are passed from a woman to all of her offspring.    
   Mitochondrial Inheritance

All of these inheritance patterns can be very confusing, and it isn't always easy to know how a specific condition is inherited. Sometimes 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 pattern, please call the nearest Genetics Department for a confidential consultation.