What is an Inherited Disease?
“An inherited trait is one that is genetically determined. Inherited traits are passed from parent to offspring according to the rules of Mendelian genetics. Most traits are not strictly determined by genes, but rather are influenced by both genes and environment” – The National Human Genome Research Institute.
Some examples of hereditary diseases include hereditary hemochromatosis, Down syndrome, spherocytosis, achondroplasia, Usher syndrome, hemophilia, sickle cell anemia, muscular dystrophy, Turner syndrome, xeroderma pigmentosum, albinism, galactosemia, neurofibromatosis, myotonic syndrome, phenylketonuria, polycystic kidney disease, retinoblastoma, Klinefelter syndrome, Tay-Sachs disease and porphyria.
Trying for a baby? Consider How Preconception Testing can help you
Our Inherited Disease screening test can be used for preconception testing of prospective parents to screen for potential overlapping genetic disorders as well as diagnosis of inherited conditions.
Preconception screening is not routinely offered and may only be discussed if there is a risk factor such as a family history or if a person belongs to a specific ethic group associated with an increased risk. However, most people don’t know they may be at increased risk so there is no easy way of determining who is at an increased risk of being a carrier for any specific gene mutation. The best approach is to have the option of preconception screening before you try to conceive. The inherited disease screening panel enables screening for a wide range of inherited diseases (expanded carrier screening), however, it does not cover every possible inherited disease. Specific diseases and genes covered are listed on the reverse. If you are discussing conception with a doctor then if preconception screening identifies you and your partner are both carriers for a condition, you will be able to consider a wider range of options. Genetic counselling may also be an option and they can provide more information about the condition and discuss reproductive choices.
Other tests which may be of interest
GTLDNA offers a genetic predisposition test which covers a total of 34 diseases. For each hereditary disease, we will assess you genetic susceptibility to the disease. Th results of such a test can help you undertake certain measures and adopt life style changes that could help towards mitigating your risk. You will, however, need to work closely with your genetic councilor. The diseases covered include some of the most important cancers, old age diseases such as Alzheimer’s as well as cardiovascular, autoimmune and general health conditions. Read more about our genetic predisposition test.
How are genetic diseases inherited?
Genetic diseases can be inherited in two very different ways which are referred to as:
- Dominant inheritance
- Recessive inheritance
In our cells, every individual has 2 copies of every chromosome with a total of 44 (22 pairs of autosomes). We must also remember the sex chromosomes – females have 2 XX chromosome pairs and males have 2 XY chromosome pairs. Each person also inherits 2 copies of every gene. Differences in the sequences of nucleotides that make up our genes can cause changes to the way they function and the proteins for which they carry instructions.
When a disorder is dominant, the child has a 50% chance of inheriting the gene from their carrier parent. The child would have 1 normal copy of the gene and another defective copy. Individuals with dominant hereditary genes have a 50% chance of passing on this gene to their children.
A recessive gene will only manifest itself in the child if he or she inherited 2 copies of the gene- one from the mother and one from the father. The child has a 25% chance of inheriting both copies of the defective gene (one copy from each parent) and a 50% chance of inheriting just one copy of the defective gene from either their mother or their father. If the child inherits just one single copy from one of their parents, they too will be carriers.