About Gene Carrier Testing

dna genetics testing

gene carrier testing

A genetic disorder is an illness or condition caused by abnormalities in your genes.

Because blood cells contain your DNA a sample can be examined to find out whether you are carrying a particular genetic mutation. this is my provides genetic testing to safeguard the future of generations to come.

gene carrier screening

Genetic screening is available to everyone. The consensus from the Human Genome Project states ”There is no legal, ethical or social reason why people should not be screened for genetic mutations before they start a family.”

Gene Carrier Screening takes blood samples from healthy person(s) who otherwise show no signs of a disorder, to see if they carry of a faulty gene or matching faulty gene.

Identifying family members who may have had a condition in the past can help determine which genetic tests may be appropriate.

who should be screened?

Most people do not know they are carriers and sadly, each year millions of parents find out only when their child is born with a serious life-threatening genetic disorder.

If you are pregnant, or are considering becoming pregnant, and are concerned about having a baby with a health problem, you may want to explore the options for genetic screening.

Some genetic disorders occur more often in certain ethnic groups. Information about the carrier frequency of the more common recessive disease traits in certain ethnic groups are provided in a table below.

results

The vast majority of screening tests are normal. If you are not found to be a carrier you cannot pass a faulty gene on. This result can provide a sense of relief from uncertainty.

However, the decision to test does require consideration, in particular what the consequences will be to you should a positive result be given. Testing is a very personal choice.

A positive screening result can help you to make informed decisions about your (future) pregnancy. At some UK IVF centres pre-implantation genetic diagnosis (PGD) is able to test an embryo for a genetic disorder before it is transferred into the mother’s womb.

  Disease Carrier frequency
Ashkenazi Jewish Tay-Sachs 1 in 30
Canavan 1 in 40
Cystic fibrosis 1 in 29
Familial Dysautonomia 1 in 30
Mediterranean Thalassemia 1 in 20 – 1 in 50
Sickle cell anemia 1 in 30 – 1 in 50
European caucasian Cystic fibrosis 1 in 29
African American Sickle cell anemia 1 in 10
Thalassemia 1 in 30 – 1 in 75
Cystic fibrosis 1 in 65
Asian Thalassemia 1 in 20 – 1 in 50
Cystic fibrosis 1 in 90
Hispanic Cystic fibrosis 1 in 46
French Canadian Tay-Sachs 1 in 15
Cystic fibrosis 1 in 29

dominant disorders

In dominant inheritance, a mutation only needs to be passed on from either the mother or the father. So, if one of the parents has the condition, there is a 1 in 2 chance it will be passed on to the child.

Huntington’s disease or neurofibromatosis, (a condition that can cause tumours to grow on nerves throughout the body) are examples of dominant diseases.

recessive disorders

In recessive inheritance, both parents must have a copy of the same faulty gene (they are both ‘carriers’ of the condition) to pass on the condition. If the child only inherits one copy of the faulty gene, they too will be a carrier of the gene but not show symptoms of the disease.

When both parents carry the same altered gene, the chance of inheriting the disease is 1 in 4 in each pregnancy.

For example, a recessive gene causes cystic fibrosis. This means a child with cystic fibrosis has inherited a faulty copy of the gene from both their mother and their father.

sex-linked disorders

If there is a mutation in a gene on the X chromosome, the effect may not be seen in females. This is because females have two X chromosomes (XX), one of which will almost certainly be normal. If a male inherits the mutation on the X chromosome from his mother, he does not have a normal copy (male chromosome is XY) and he will develop the condition.

The chance of inheriting the altered gene is 1 in 2 in each pregnancy for both boys and girls, but only male offspring will be affected.

Both Duchenne muscular dystrophy and haemophilia are inherited in this way.

dna genetics dominant chromosomes
dna genetics recessive chromosomes
dna genetics sex lined genes