Affected Individual: An individual who has a particular trait or disease. The individual expresses the trait or has signs and symptoms of the disease, which is called the “phenotype.”
Allele: A version of a DNA sequence. Most inherited differences between individuals are the result of genetic differences at a specific location in the genome. These differences are called alleles. There may be many different alleles for the same location, but an individual inherits only two alleles, one from each parent, for any given genomic location.
Amino Acid: An amino acid is the molecule that serves as the building block for proteins. There are 20 different amino acids used in human proteins. A protein consists of one or more chains of amino acids (called polypeptides). The sequence of amino acids in a polypeptide is encoded in the DNA of a gene. Some amino acids can be synthesized in the body, but others (essential amino acids) cannot and must be obtained from a person’s diet.
Autosome: Any chromosome that is not a sex chromosome.
Autosomal Recessive: One of the ways a genetic trait or a genetic condition can be inherited. Autosomal means that the disease gene is located on the numbered, or non-sex chromosomes (1-22). Recessive means that two copies of the mutated gene or region (one from each biological parent) are required to cause the disorder/disease. An example of an autosomal recessive disorder is cystic fibrosis.
Autosomal Dominant: One of the ways a genetic trait or a genetic condition can be inherited. Autosomal means that the disease gene is located on the numbered, or non-sex chromosomes (1-22). Dominant means that only one copy of the mutated gene or region (from a biological parent) is required to cause the disorder/disease. An example of an autosomal dominant disorder is Marfan syndrome.
Base Pair: Two complementary bases in a double-stranded nucleic acid molecule (DNA), consisting of a purine (adenine and guanine) in one strand linked by hydrogen bonds to a pyrimidine (cytosine and thymine) in the other. Cytosine always pairs with guanine, and adenine with thymine.
Base Sequence: The sequence of purines (adenine or guanine) and pyrimidines (cytosine and thymine) in DNA. The order of bases is represented as a string of As, Cs, Gs, and Ts.
Benign: A DNA variant that does not lead to known genetic conditions.
Biomarker: A biological molecule found in blood, other body fluids, or tissues that indicates a normal or abnormal process, or a condition or disease. A biomarker may be used to diagnose a disease or condition, or to see how well the body responds to a treatment. May also be called molecular marker or signature molecule.
Cancer: Cancer is a disease in which some of the body’s cells grow uncontrollably. There are many different types of cancer, and each begins when a single cell acquires a genomic change (or mutation) that allows the cell to divide and multiply unchecked. Additional mutations can cause the cancer to spread to other sites in the body. Cancer mutations are usually not inherited, but rather caused by errors during DNA replication or result from DNA damage due to environmental exposures (such as tobacco smok