| 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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