Do you look a lot like the people in your family? I do too. Most people know this is because of genes we inherited from our parents. Some health problems are also passed down through families genes. I have two children who were born with two different autosomal recessive diseases, Miller syndrome, and primary ciliary dyskinesia, PCD.
However, for 33 years we didn’t know that two different autosomal recessive genes caused their conditions. In 2010, scientists sequenced our entire genome (all our genes). Fortunately, they found the genes that caused my children’s diseases.
Autosomal Recessive Disease
To have a child born with an “autosomal recessive disease” both you and your partner must have a mutated gene. Furthermore, you must both pass those genes on to your child.
This means that Heather and Logan‘s father (Terry), and I, both each carry a copy of both the Miller syndrome gene and the PCD gene. Heather and Logan, each, got two copies of each of the genes. They each got one Miller gene from mom and one from dad, and they each got one PCD gene from mom and one from dad.
Both Heather and Logan each got two copies of the Miller syndrome gene and two copies of the PCD gene. As a result, they both have both of the autosomal recessive diseases.
The odds of this happening are only 1 in 10, billion!
What is a Dominant Gene?
Some genes are “dominant.” You only need one from a parent to have that trait.
What is a Recessive Gene?
Other genes are “recessive.” With them, you have to inherit the same gene from both parents to be affected, as I described above.
If one of your parents passes on a recessive gene to you that can cause disease, then you become a “carrier.” Terry and I are carriers of both of the disease-causing genes.
When you’re a carrier, you don’t have any symptoms, since the other gene is normal. In fact, many people won’t know they’re a carrier without being tested.
A Child has a 25% Chance of Inheriting a Recessive Gene from a Parent
If you and your partner both have the same mutated gene, there’s a 25% chance that your child will be born with a severe disease. Anyone can carry a recessive gene that causes illness.
This risk exists for each pregnancy between these two parents. As a result, two carriers of a recessive gene gives their child a 25% chance of inheriting a copy of the Miller syndrome gene from both mom and dad, resulting in the child having Miller syndrome.
However, Miller syndrome is extremely rare. Currently, there are only 30 cases documented, worldwide, in the medical literature. The chances of a person having Miller syndrome is 1 in one million.
Two carriers of the PCD gene also gives their child a risk of 25% chance of inheriting a copy of the PCD gene from both mom and dad, resulting in the child having lung disease. The chances of a person having PCD is 1 in 10,000.
