What is a Gene?
To understand what genes are, it is helpful to know where they are in the body. Our bodies are made of cells. These cells are fluid filled sacs that are so small you cannot see them with just your eye. You would need a microscope. More...

How do genes cause or contribute to disease?
There are many ways genetic differences can affect the way the body functions. The genetic difference may cause the body to make something incorrectly, make too much of something, or make something when it is not needed. More...

Single Gene Disorders
When a certain gene is known to cause a disease, we refer to it as a single gene disorder or a Mendelian disorder. For example, you may have heard of cystic fibrosis, sickle cell disease, Fragile X syndrome, muscular dystrophy, or Huntington disease. These are all examples of single gene disorders. More...

Genes and Complex Disorders
Most disorders are categorized as complex. These disorders do not follow the same predicted pattern of inheritance seen in single gene disorders. Instead, they result from a complex interplay of genes and environment. More...

Genes and Environmental Disorders
Most disorders in this category are infectious diseases such as tuberculosis or HIV.  While a person cannot have the disease without exposure to the infectious organism, genetics does play a role in who will become sick and how ill they will become. More...

How do Scientists Search for Genes?
Looking for a gene is a difficult task and often takes years to accomplish. Scientists use maps of the chromosomes (similar to a road map) to look for genes. Searching for genes that cause a specific disorder is somewhat like trying to find a street on a map of the world. More...

How do Markers Help Find Genes that Cause Disorders?
Scientists test many different markers on all the chromosomes, trying to find markers that are consistently found in people who have a particular disorder more frequently than those without the disorder. More...

What are candidate genes and how do they help scientists?
Candidate genes are genes that scientists think may contribute to a disorder either because of where they are located, because of what they do, or both. In situations where the scientists think they know the small region of the chromosome where a gene might be from other studies, they look at the genes in that region. More...

What are copy number variants and how do they help scientists?
Copy Number Variant or CNVs are a complex form of genetic variation where DNA is present in greater or less amounts in an individual compared with the average population. CNVs are caused by a deletion or duplication of DNA segments and are the largest single source of variation among individuals. More...