I am currently pregnant and I'm wondering how high are the chances of my baby being an albino. My husband's father is an albino and I'm guessing that means he carries the gene. As far I know we do not carry that trait in my family.
What are the chances of having an albino baby if the mother does not have the trait and the father does? What are the chances if both parents carry the trait?
-A curious adult from Virginia
February 11, 2010
Without a genetic test, it is impossible to figure out your baby's risk for getting albinism. This is because of how most forms of albinism are passed down.
To show up, albinism usually has to be passed from both sides of the family. In this case, we know the baby's dad probably carries a version of a gene that can cause albinism. He most likely inherited it from his dad. (I talk about a rare exception in the last section of the answer where the baby's dad would not be a carrier.)
But we don't know about the baby's mom because there is no history of albinism in her family. She may carry a version of an albinism gene and she may not. That is where a genetic test might help.
If both parents do carry an albinism gene version, then each child would have around a 25% chance of having albinism. If the mom doesn't carry this gene version, then the chances are very low that any of her kids will have the condition.
What I thought I'd do for the rest of the answer is go into a little more detail about where I got these numbers. To understand this, we need to take a step back and go over what albinism is.
Albinism is an Absence of Pigment
Albinism happens when certain cells in our bodies can't make the pigment melanin. This pigment gives darker skin and hair colors. And most eye colors other than blue.
Melanin is more than just looks. It is responsible for the way our skin reacts to the sun. It is also needed in order for our eyes to see well. This is why people with albinism sunburn so easily and have vision problems.
There are different types of albinism. Some people only have problems with their eyes. For others, their eyes, skin, and hair are affected. The type of albinism someone has depends on what's in their DNA.
Back up Gene Copies
Our DNA is stored in structures called chromosomes. Each of the cells in our body contains 46 of them.
We got half of these chromosomes from our mom and the other half from our dad. This is a key way each of us becomes a unique combination of our parents.
Every chromosome contains many genes. And each gene has the information for one small part of you. The genes we're interested in are those that are involved in making pigment.
If we look closely at our chromosomes we will see that they can be matched up in pairs of two. Why do we have 23 pairs of chromosomes? Because we've inherited the same chromosomes from our mom and dad. Which means we have two copies of most of our genes too.
This gives us a back up system. If we have a difference or a mutation in one of our genes, we have another copy that can do the same job.
Sometimes the back up copy can do enough work to make up for the change. In this case, we'll never know we have something there that can cause a problem. But other times, we need both copies of the gene on a chromosome to work.
Most forms of albinism need both copies to have a change that can lead to albinism. In other words, we need to get a chromosome from each parent with a version of a gene that will lead to albinism.
Answering Your Question
As I said before, most cases of albinism need to be passed down from both sides of the family. Assuming this is the case with your husband's father, he must have inherited a genetic difference from both his mother and his father. Because of this, he has albinism.
But what does this mean for your child? Your child would have to inherit a gene that can lead to albinism from both your husband and you.
Because your husband's father has been diagnosed with albinism, we know that most likely one of your husband's chromosomes has a gene with the difference that can lead to albinism. Since he doesn't have albinism himself, we know that his other copy does not have that difference.
We don't have any information about your side of the family. Because albinism can be hidden, you may or may not carry a gene that can lead to albinism. We cannot know if you carry such a change without checking your DNA.
Let's say that we checked your DNA and found that you do not carry any changes that might cause albinism. In this case, there is very little chance your child would be diagnosed with albinism. The child will have a 50% chance of carrying a gene from your husband that can lead to albinism but that would not be enough to cause albinism.
On the other hand, if we checked your DNA and did find a change, then your child would have up to a 25% chance of being diagnosed with albinism. Why? We know your child has a 50% chance of inheriting the genetic difference for albinism from your husband. If you have it too, then you have a 50% chance of passing it on. Put these two together and you end up with a 25% chance of both of you passing it on at the same time.
A Different Type of Albinism
What we've talked about so far are cases of albinism that have to come from both sides of the family. There are some types that are passed down in a different way.
One way is by something we call X-linked inheritance. This type of albinism happens less often and usually only affects the eyes.
X-linked inheritance means the genetic change that causes albinism is found on the X chromosome. The X chromosome helps to decide whether we will be male or female. Females have two X chromosomes while males have just one X chromosome (paired with a Y chromosome).
If a father has X-linked albinism, none of his sons will inherit the genetic change linked to albinism. Why is that? Because fathers do not give their sons X chromosomes.
Fathers always give their sons a Y chromosome. And, since the mutation for albinism in on the X chromosome, a son cannot inherit it from his dad.
If a woman's dad has X-linked albinism, she will inherit her dad's mutation " always. But, most of these daughters will not see any effects of the genetic change. They can pass that change on the X chromosome to 50% of their children though. So when it is time for them to have kids, they will need to remember this.
It is possible that your father-in-law has X-linked albinism. He could have inherited a genetic change from his mother on the X chromosome. If this is the case, your husband does not have that genetic change. And your child could not inherit albinism from his father or grandfather.