What is a Genetic Condition?
Disclaimer: I am not a doctor and I don’t pretend to be. This is my understanding of genetic conditions from my research.
Every person has two copies of most genes – one from each parent.
A person is a ‘carrier’ when they have inherited one copy of a faulty gene (a gene mutation) associated with a genetic condition, but their other copy of the gene is functioning normally so can take over. They won’t have the genetic condition themselves but will be a ‘carrier’ of the condition.
A carrier can pass on this faulty gene or genes to their children. When a faulty gene associated with a genetic condition is passed on to a child by each parent – this means the child has two faulty genes and no healthy copy – the child will have the genetic condition.
It is estimated that all people are carriers of several recessive genetic conditions, without ever realising it. Isn’t that scary! That statistics I have seen says that we all carry 3-5 genetic disorders in our DNA which you can pass on to your children.
There are a few ways genetic conditions can be passed on including dominant genetic disorders, x-linked genetic disorders etc. but the most common way is as recessive genetic condition like SMA. That is when two people who carry a fault in a gene for the same condition have children. With a recessive genetic condition, when two partners get together and have a child there are a few outcomes that can happen. There is a 1 in 4 (25%) chance that their child will inherit faulty copies of the gene from both parents, and have the genetic condition, a 25% chance that the child will be unaffected and a 50% chance that the child will be a carrier like their parents.
As I said there are other inheritance patterns other than recessive genetic disorders, such as X-linked conditions like Fragile X syndrome (FSX). There, women have two X chromosomes and men have one X and one Y. If there is a faulty gene on the X chromosome it can cause a genetic condition. Usually boys and men are more severely affected by X-linked conditions than girls and women – women may be healthy carriers who do not show any signs of the conditions but may show symptoms later in life. In the case of X-lined conditions, or dominant conditions, a couple having children have a 50% chance of having an affected child.
SMA is one of thousands of genetic disorders, most people haven’t heard of SMA but one you may have heard of is Cystic Fibrosis (CF). Some genetic conditions are lethal and severe whilst others can be mild, and you can live with them or some which have treatments. Like most things in life the genetic conditions range from ‘ok’ to life shattering. Genetics is such a scary world but it is real.
Whilst the world of genetic can be scary, it is real; and if we are strong enough to pay attention and not run away scared, there is actually something we can do to protect our children. We can learn about our own individual genetic faults and our chances of passing them on to our children. This is done through a test called ‘genetic carrier screening test’ or ‘reproductive genetic screening’.
Without this testing or a family history most, people will never know they carry a genetic condition until they have an affected child, or someone they are related to does.
If knowing that we all carry genetic disorders we can pass on doesn’t scare you. Think about this - a study by the Murdoch Children’s Research Institute showed that one in twenty people tested will carry either SMA, CF or Fragile X (FXS), that isn’t even thinking about the other thousand or so genetic conditions. This is the same prevalence as Down Syndrome. We routinely test for Down Syndrome, so why don’t we routinely test for these recessive genetic disorders, especially if they are fatal?
Genetic conditions are NOT the same as chromosome conditions! Genetics are held within our chromosomes but they are not the same thing which means the test for chromosome issues is not testing for your genetics. Your NIPT/Harmony/Genesyte test does not look at the genetic conditions you carry. They look at chromosomes.
See my next blog post on how to get genetic testing in Australia.