|
Serving Individuals and Families
Genetics Information: Inheritance
What are patterns of inheritance
Patterns of inheritance refer to the way a genetic disorder is passed
on through the family. These depend on the gene involved in the disorder
and on which chromosome the gene is located. For example, an "autosomal"
disorder refers to a disorder that is caused by a gene located on one
of the numbered chromosomes (1-22). Both males and females are affected
equally in autosomal disorders. An "X-linked" or "sex-linked"
disorder refers to a disorder caused by a gene located on the X chromosome.
X-linked disorders typically affect males much more often than females.
How are primary immune deficiency disorders inherited?
Because there are at least 100 different types of PI disorders, there
are at least that many genes responsible for these disorders. Therefore,
the pattern of inheritance depends on the PI disorder and the gene involved.
For a detailed explanation of inheritance patterns, refer to the chapter
on Inheritance in the Patient
and Family Handbook. To determine which pattern of inheritance your PI
disorder follows, go to the appropriate chapter in the Patient
and Family Handbook.
If one family member has a primary immune deficiency
disorder, is it likely that other family members will also have it?
The risk of having a primary immune deficiency disease is higher in family
members of an affected patient. This increased risk depends on the type
of primary immune deficiency disorder and the manner in which the genetic
defect is inherited. It is most important to identify the specific genetic
defect and that will provide information as to how the disease is inherited
and who else in the family may be at risk of having the disorder. Again,
please refer to the Inheritance
chapter in the Patient and Family Handbook for more information.
If primary immune deficiency disorders are genetic,
or congenital, why is it that some of these defects are diagnosed in adults?
It is possible that these defects are present all along, but not diagnosed
due to compensating immune functions that keep serious problems from developing
earlier. It is also possible that there is a slowly deteriorating immune
function, genetically determined, that does not become significant until
later in life.
How long will a primary immune deficiency disorder
stay within a family's gene pool?
Genes may be passed on to any of our offspring, but how they are passed
on and to which child depends on the way the gene is inherited and expressed.
Usually, a specific gene is only passed on to some of the children, but
not all. If the gene for a primary immune deficiency disorder is passed
on from parent to child, it may then be passed on from that child to some
of their children and so on and so on. At each generation, there is some
chance that the gene may be passed on. Therefore, a gene for a primary
immune deficiency disorder, like any other gene, can stay in a family's
gene pool for many generations.
|
