If you have diabetes, why your brother or sister might also have it—or not.

If this is your family tree, who has diabetes? And who will get diabetes? The answer to that questions is, "It's in the genes." But what does that mean? Let's look beneath the surface to find out.

You are made up of genes, anywhere from 30,000 to 66,000 of them. These infinitesimal bits of data give instructions to all the cells of your body. Those instructions dictate how your body will look, grow, and be.

As you live, your cells divide and your genes replicate in the process, continuing to give the messages that make you, well, happen.

Genes are an interesting fact of life. Let's take a look at exactly how they work and try to answer a practical question that nags many kids with diabetes. Why did I have to get it? And why doesn't my brother or sister have it? Or, as with brothers Eric and Alex Bonness, and perhaps more interesting to scientific researchers: Why did my brother get it, too?

The Diabetes Genes
Type 1, or "juvenile," diabetes can result when certain combinations of gene variants are inherited. As many as 10 or more genes are thought to be involved.

This means that you must have just the right combination of genes to be susceptible to developing diabetes—and it means that your parents, either one or both, had to supply that combination. They would have inherited these genes from their parents, and so on.

There are an infinite number of possible gene combinations, each resulting in completely unique individuals that are you and your brothers and sisters. It's why there are no two people who are exactly the same (unless you have a twin with identical genes)! It's also why you may have diabetes, and your siblings may not.

Environmental Factors
Now it's time to complicate things. Guess what? Genes don't quite tell the whole story of why you got diabetes.

You may have the correct combination of genes to be at risk for diabetes, but scientists believe it takes an environmental trigger, or perhaps many triggers, to cause it to develop. By "environmental," they mean something — anything — around you that affects you, but not something you were born with. It could be as simple as the food you eat, as mysterious as a virus you may have contracted, or as puzzling as where you live.

The triggering concept is a difficult one to grasp. Indeed, it confounds scientists. Why would diabetes develop in one identical twin, for example, but not the other? It happens all the time, yet they have the same sets of genes and, often, the same basic surroundings. That just shows how complicated the notion of environment and genes is.

Putting the Pieces Together
Amazingly, for about 90 percent of people with type 1 diabetes, the disease doesn't exist elsewhere in their families! This could be because no one else received that combination of genes. It could also be because others have the combination but never encountered a trigger.

Conversely, there are plenty of families, like the Bonnesses, in which more than one family member has type 1 diabetes. Genes are most certainly underlying this occurrence, and environment, too.

Gene Science
Scientists around the world have been working for more than a decade to produce a "map" of the human genome. The location of each gene on a given chromosome is consistent from person to person. Basically, for each of the 23 chromosome pairs we humans possess, researchers wanted to figure out where genes governing various processes are located.

This map finally has been completed. As it has developed, it has been tremendously helpful in the search for a cure for diabetes. Now we know that there are several "regions" of genes, on several different chromosomes, that are linked to diabetes susceptibility.

For example, a region of genes on Chromosome 6 is involved in type 1 diabetes. Chromosomes 10 and 16 are also linked to type 1 diabetes. (In contrast, Chromosomes 1 and 20 are implicated in type 2 diabetes.) There are now believed to be at least 10 genetic regions, or loci, that are linked to type 1 diabetes.

Researchers are using genetic information to develop therapies and treatments that can one day be used to prevent or slow down the development of diabetes—for a sibling or a child of yours, perhaps! This information may also be tremendously helpful in eliminating the problems that diabetes can cause, such as kidney trouble. Why? You guessed it: Kidney disease is also linked to genes.