Advocacy in Genetics: A Teaching Guide and Workbook
Glossary of Genetic Terms
Abnormal: A variation from the normal. In the case of genes an abnormal gene may result in a specific disorder.
Acquired mutations: Gene changes that arise within individual cells and accumulate throughout a person’s lifetime; also called somatic mutations.
Age of onset: Age at which the effects of a genotype become evident.
Adenine (A): A base; one of the molecular components of DNA and RNA.
Advanced maternal age: Women over age 34 (age 35 at delivery) are at increased risk for nondisjunction trisomy in the fetus.
AFP (Alpha-fetoprotein): A protein excreted by the fetus into the amniotic fluid and from there into the mother's bloodstream through the placenta.
Alleles: Any one of two or more alternate forms of a gene located at the same locus.
Allelic (gene) frequency: The percentage of alleles (genes) in a population that are of a particular type.
Amino acids: Small molecules that form the building blocks of proteins.
Amniocentesis: Prenatal diagnosis method using cells in the amniotic fluid to determine the number and kind of chromosomes of the fetus and, when indicated, perform biochemical studies.
Amplification: Production of multiple copies of a sequence of DNA.
Anencephaly: One of a series of defects in which the tube of tissue destined to form the brain and spinal cord fails to close, in this case resulting in absence of brain, skull cap, and scalp.
Aneuploidy: State of having a variant chromosome number (too many or too few). (i.e., Down syndrome, Turner syndrome).
Anomaly: Deviation from the average; anything unusual, irregular or contrary to the general rule.
Anticipation: Onset of an inherited disorder at an earlier age, or worsening of symptoms in successive generations.
Artificial insemination: The placement of sperm into a female reproductive tract or the mixing of male and female gametes by other than natural means.
Autosome: Any chromosome that is not part of the pair of sex chromosomes. Humans have twenty-two pairs of autosomes, numbered from 1 to 22.
Autosomal Dominant Trait: Refers to how a disease, condition, or trait is inherited. (Autosomal) the gene involved with the disease is located on a chromosome other than X or Y (sex chromosomes). Therefore the gene will be located on chromosome 1 to 22. (Dominant) all genes occur in pairs. In autosomal dominant conditions, if one of the genes in a pair is not working the disease will be present, it does not matter that the other gene in the pair is functional. Males and females are equally affected. If an individual has a nonfunctional gene, each of his/her children has a 50% chance of inheriting it. Examples of dominant diseases include Huntingtons disease, neurofibromatosis, and most inherited cancers..
Autosomal Recessive Trait: Refers to how a disease, condition, or trait is inherited. (Autosomal) the gene involved with the disease is located on a chromosome other than the X or Y (sex chromosomes). Therefore the gene will be located on chromosome 1 to 22. (Recessive) all genes occur in pairs. In autosomal recessive condition, if one of the genes in a pair is not working, the functional gene is enough to prevent the disease. The condition only occurs when an individual inherits two nonfunctional genes. Men and women are equally affected. If a couple carry the same nonfunctional gene, for each pregnancy, they have a 25% chance of having an affected child, a 50% chance to have a child who is carrier, and a 25% chance to have a child who is not affected and not a carrier. Examples of recessive diseases include cystic fibrosis and sickle cell disease.
Autosome: All chromosomes except those involved in sex determination. Human cells have 22 pairs of autosomes.
Balanced Translocation: Occurs when two chromosomes break and exchange places, leaving the same amount of genetic material. An individual with a balanced translocation will be unaffected, but their children may be affected in a variety of ways.
Bases: The molecular building blocks of DNA and RNA: adenine, cytosine, guanine, thymine, and (in RNA only) uracil. In DNA, A attaches only to T, and C attaches only to G. In RNA, A attaches only to U, and C attaches only to G. Two strands of DNA are held together in the shape of a double helix by weak chemical bonds between their base pairs.
Base pair: Two of the building blocks of DNA held together by weak bonds. In a DNA molecule, adenine always bonds with thymine (A-T), and cytosine always bonds with guanine (C-G).
Base sequence: The order of bases in a DNA molecule.
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