| Single Gene
Disorders and Disability (SGDD) |
A mutation is any
change in the usual DNA sequence. For example, suppose part of a gene
usually has the sequence
GTAC. A mutation can change the sequence
to
GTTC in some people. This change in
sequence can change the way that the gene works so that people with this
mutation can have a particular condition. Some mutations do not seem to
affect the person who has them.
Genetic conditions
are often described in terms of the chromosome that contains the gene. If
the gene is on one of the first 22 pairs of chromosomes, called the
autosomes, the genetic condition is called an “autosomal” condition. If the
gene is on the X chromosome, the condition is called “X-linked”.
Genetic conditions
are also grouped by how they run in families. Different mutations cause
conditions to run in families with different patterns. Mutations are called
“dominant” or “recessive” depending on how they cause conditions and how
they run in families.
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Date: September 1, 2006
Content source: National Center on Birth Defects and Developmental
Disabilities
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