Genes and You

Most families don’t need to worry about the genetic instructions they will pass on to their children. But in some circumstances the genes aren’t working properly and might cause developmental problems.

Here’s some information that will help you understand genetics and the issues some families face.

Below are 3 examples of how genes are passed on to the children in a family.

FAMILY 1 - Healthy Carrier + Healthy Carrier

Family 1
Both parents are healthy carriers of the changed gene. Their children will either inherit the healthy gene or the changed gene from each parent and this is at complete random.

When the mother is pregnant there is a 25% chance (1 in 4) that the child will inherit one healthy copy from mum and one healthy copy from dad. This means they will be healthy and NOT a carrier and so will not suffer from the recessive condition and will not be at risk of passing it onto their future children.

There is a 50% (2 in 4) chance that the child will inherit one healthy copy from either mum or dad and one changed gene from the other parent and so will be a healthy carrier. They will not suffer from the recessive genetic condition however as the child has one changed gene so they will be a healthy carrier like their parents and may be at risk of passing it onto their children in the future.

There is a 25% chance (1 in 4) that the child will inherit a changed gene from both mum and from dad and so this child will suffer from the recessive genetic condition. This is because they have 2 copies of the changed gene.

FAMILY 2 - Healthy Carrier + Not a Carrier

Family 2
One parent is a healthy carrier and so will either pass on a healthy gene or a changed gene. The other parent has no copies of the changed gene and so can only pass on a healthy gene.

When the mother is pregnant the children will have a 50% chance of inheriting one changed gene and one healthy one. This will mean they are healthy carriers and will not be affected by the recessive condition but may be at risk of passing it on to their future children.

There is a 50% chance that the child will inherit one healthy copy from mum and one healthy copy from dad. This means they will be healthy and NOT a carrier and so will not suffer from the recessive condition and will not be at risk of passing it onto their future children.

FAMILY 3 - Person with Condition X + Not a Carrier

Family 3
As one parent has the recessive condition they have two copies of the changed gene and so can only pass on a changed gene. However their partner is healthy and has no changed genes and so ALL of their children will receive one changed gene and one healthy one. This pattern will be consistent throughout all pregnancies. This means they will all be healthy carriers and not suffer from the recessive genetic condition however as the child has one changed gene they may be at risk of passing it onto their children in the future.

If a healthy carrier is going to marry someone within the extended family, then it would be advised that the partner should also be tested.