What are genes?
Genes are the
part of a body cell that contain the biological information that parents pass
to their children. Genes control the growth and development of cells. Genes are
DNA (deoxyribonucleic acid), a substance inside the
center (nucleus) of cells that contains instructions for the development of the
You inherit half of your genetic information from your
mother and the other half from your father. Genes, alone or in combination,
determine what features (genetic traits) a person inherits from his or her
parents, such as blood type, hair color, eye color, and other characteristics,
including risks of developing certain diseases. Certain changes in genes or
chromosomes may cause problems in various body
processes or functions.
What are chromosomes?
Many genes together make up
larger structures within the cell called chromosomes. Each cell normally
contains 23 pairs of chromosomes.
human has 46 chromosomes (23 pairs). One chromosome from each pair comes from
the mother, and one chromosome from each pair comes from the father. One of the
23 pairs determines your sex. These sex chromosomes are called X and Y.
- For a child to be female, she must inherit an
X chromosome from each parent (XX).
- For a child to be male, he must
inherit an X chromosome from his mother and a Y chromosome from his father
genetic disorders are caused when all or part of a
chromosome is missing or when an extra chromosome or chromosome fragment is
What is genetic testing?
Genetic testing examines
a DNA sample for gene changes, or it may analyze the number, arrangement, and
characteristics of the chromosomes. Testing may be performed on samples of
blood, semen, urine, saliva, stool, body tissues, bone, or hair.
Should I have genetic testing?
You may choose to
have genetic testing if you are concerned that you have an increased risk for
having or getting a disease that has a genetic cause. The information you
obtain from the tests may help you make decisions about your life. For example:
- If tests show that you have an increased
risk for passing on a disease to your child, you may choose to have more
genetic testing while you are pregnant (prenatal testing). Or you may decide to
adopt a child.
- If tests show that you have an increased risk
for developing a disease such as
breast cancer, you may make decisions that help lower
your risk of breast cancer.
- You may feel reassured if the tests
You may decide to have a genetic test during pregnancy to
find out whether your
fetus has a disorder, such as
Down syndrome. Information obtained from the test can
help you decide how to manage your pregnancy.