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Genetics Overview
What is a Candidate Gene?
 A candidate gene is a gene that researchers think may be related to a
particular disease or condition. Researchers find candidate genes in a variety of different ways,
but candidate genes in general may be divided into two categories: positional or functional.
- Positional candidate genes
A positional candidate gene is one that researchers think may be associated with a disorder based
on the gene's location on a chromosome. When a region on a chromosome is shown to be "linked" with
autism (because a part of that region shows up more frequently in individuals with autism than in
the general population), researchers begin looking closely at the genes that have already been
identified in that region. Thanks to the Human Genome Project and related research, many genes
have already been identified or mapped. This information is available to researchers through
different databases. Researchers may also focus in on genes in a particular chromosomal region if
there are individuals with a disorder who also have chromosome abnormalities in that region. For
example, because many individuals with autism have duplications of a region of chromosome 15,
researchers have looked for candidate genes in that region.
- Functional candidate genes
Researchers sometimes look at candidate genes that make products that may have something in common
medically or biologically with the disorder that they are studying. For example, earlier research
has shown that some people with autism have higher than average levels of serotonin (a chemical
called a neurotransmitter which sends messages between brain cells) in their blood. Because of what
is already known about the connection between serotonin and autism, researchers consider the serotonin
transport gene a good candidate gene. Although many groups have had inconsistent findings as to
whether this gene plays a role in the development of autism, researchers are still examining its
possibilities.
More ...
It is important to note that researchers may study many different candidate genes before identifying
genes that are associated with a particular disorder. In many instances a research group will report
significant findings with a particular candidate gene, but another group trying to repeat the findings
will be unsuccessful or even find opposite results. Therefore the process of finding and confirming
candidate genes may take quite some time.
Autistic disorder Candidate Gene References
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WHAT IS A GENE?
Genes are very small structures inside almost every cell of
the body. They are the instructions, or blueprints, that tell
our body how to grow and develop, build necessary proteins,
and thus determine an individual's characteristics, such as
eye color and blood type. More ...
HOW GENES ARE NAMED
You may wonder how genes are named. As you may have guessed,
some names are abbreviations for the full gene names. Other
genes are named after similar genes in other organisms. More ...
WHAT IS A CHROMOSOME?
Chromosomes are structures that contain genes. Chromosomes are
visible with a microscope and are located in the nucleus of a
cell. Almost every human chromosome contains thousands of individuals
genes. More ...
HOW CHROMOSOME ABNORMALITIES HELP US FIND GENES
Genetic researchers use many different tools and strategies to
look at the genetic material (DNA) inside our cells to find the
exact gene(s) that cause a genetic disorder such as autism. More ...
HOW GENOME SCREENS HELP US FIND GENES
In order to determine the genes that may be involved, scientists
also perform what are referred to as "genome screens." To do this
they use maps of the chromosomes in order to look for genes. More ...
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