Rhode Island Department of Health Genetics Website

Glossary

 Alleles:

variant forms of the same gene. Different alleles produce variations in inherited characteristics such as eye color or blood type.

Alzheimer's disease:

a disease that causes memory loss, personality changes, dementia and, ultimately, death. Not all cases are inherited, but genes have been found for familial forms of Alzheimer's disease.

Amino acid:

any of a class of 20 molecules that combine to form proteins in living things.

Base pairs:

the two complementary, nitrogen-rich molecules held together by weak chemical bonds. Two strands of DNA are held together in the shape of a double helix by the bonds between their base pairs. (See Chemical base.)

BRCA1 breast cancer susceptibility gene:

a mutated version of the BRCA1 gene, which predisposes a person toward developing breast and ovarian cancer.

Carrier:

a person who has a recessive mutated gene, together with its normal allele. Carriers do not usually develop disease but can pass the mutated gene on to their children.

Carrier testing:

testing to identify individuals who carry disease-causing recessive genes that could be inherited by their children. Carrier testing is designed for healthy people who have no symptoms of disease, but who are known to be at high risk because of family history.

Cell:

small, watery, membrane-bound compartment filled with chemicals; the basic subunit of any living thing.

Chemical base:

an essential building block. DNA contains four complementary bases: adenine, which pairs with thymine, and cytosine, which pairs with guanine. In RNA, thymine is replaced by uracil.

Chromosomes:

structures found in the nucleus of a cell, which contain the genes. Chromosomes come in pairs, and a normal human cell contains 46 chromosomes.

Cleft Lip:

is a condition that creates an opening in the upper lip between the mouth and nose

Cleft Palate:

occurs when the roof of the mouth has not joined completely.

Cystic fibrosis:

an inherited disease in which a thick mucus clogs the lungs and blocks the ducts of the pancreas.

DNA:

the substance of heredity; a large molecule that carries the genetic information that cells need to replicate and to produce proteins.

DNA sequencing:

determining the exact order of the base pairs in a segment of DNA.

Diabetes:

A condition where the body doesn't make enough insulin or can't use its own insulin as well as it should and causes sugars to build up in the blood.

Dominant allele:

a gene that is expressed, regardless of whether its counterpart allele on the other chromosome is dominant or recessive. Autosomal dominant disorders are produced by a single mutated dominant allele, even though its corresponding allele is normal. (See Recessive allele.)

Down syndrome

a genetic condition caused by extra genetic material (genes) from the 21st chromosome.

Enzyme:

a protein that facilitates a specific chemical reaction.

Familial cancer:

cancer, or a predisposition toward cancer, that runs in families.

Gene:

a unit of inheritance; a working subunit of DNA. Each of the body's 30,000 to 40,000 genes contains the code for a specific product, typically, a protein such as an enzyme.

Gene expression:

the process by which a gene's coded information is translated into the structures present and operating in the cell (either proteins or RNAs).

Gene markers:

landmarks for a target gene, either detectable traits that are inherited along with the gene, or distinctive segments of DNA.

Gene mapping:

determining the relative positions of genes on a chromosome and the distance between them.  

Gene testing:

examining a sample of blood or other body fluid or tissue for biochemical, chromosomal, or genetic markers that indicate the presence or absence of genetic disease.

Gene therapy:

treating disease by replacing, manipulating, or supplementing nonfunctional genes.

Genetic counselor:

Person trained to discuss decisions regarding genetic testing and its implications with a patient and their families

Genetics:

the scientific study of heredity: how particular qualities or traits are transmitted from parents to offspring.

Genome:

all the genetic material in the chromosomes of a particular organism.

Genome maps:

charts that indicate the ordered arrangement of the genes or other DNA markers within the chromosomes.

Genomics:

the study of all of the genes in an organism (or genome).

Genotype:

the actual genes carried by an individual (as distinct from phenotype; that is, the physical characteristics into which genes are translated).

Human genome:

the full collection of genes needed to produce a human being.

Human Genome Project:

an international research effort (led in the United States by the National Institutes of Health and the Department of Energy) aimed at identifying and ordering every base in the human genome.

Huntington's disease:

an adult-onset disease characterized by progressive mental and physical deterioration; it is caused by an inherited dominant gene mutation.

Inborn errors of metabolism:

inherited diseases resulting from alterations in genes that code for enzymes.

Inheritance:

Transmitted through genes from parents to offspring.

Leukemia:

cancer that begins in developing blood cells in the bone marrow.

Molecule:

a group of atoms arranged to interact in a particular way; one molecule of any substance is the smallest physical unit of that particular substance.

Mutation:

a change in the number, arrangement, or molecular sequence of a gene.

Newborn screening:

examining blood samples from a newborn infant to detect disease-related abnormalities or deficiencies in gene products.

Nucleotide:

A subunit of DNA or RNA, consisting of one chemical base plus a phosphate molecule and a sugar molecule.

Parkinson's Disease:

an imbalance of dopamine and acetylcholine that causes a lack of coordination in movement that often appears as tremor, stiff muscles and joints, and/or difficulty moving.

Phenylketonuria (PKU):

an inborn error of metabolism caused by the lack of an enzyme, resulting in abnormally high levels of the amino acid phenylalanine; untreated, PKU can lead to severe, progressive mental retardation.

Predictive gene tests:

tests to identify gene abnormalities that may make a person susceptible to certain diseases or disorders.

Prenatal diagnosis:

examining fetal cells taken from the amniotic fluid, the primitive placenta (chorion), or the umbilical cord for biochemical, chromosomal, or gene alterations.

Protein:

a large, complex molecule composed of amino acids. The sequence of the amino acids and the function of the protein is determined by the sequence of the base pairs in the gene that encodes it. Proteins are essential to the structure, function, and regulation of the body. Examples are hormones, enzymes, and antibodies.

Pyloric Stenosis:

the narrowing of part of the stomach (the pylorus) that leads into the small intestines and causes projectile vomiting

Recessive allele:

a gene that is expressed only when its counterpart allele on the matching chromosome is also recessive (not dominant). Autosomal recessive disorders develop in persons who receive two copies of the mutant gene, one from each parent who is a carrier. (See Dominant allele.)

Screening:

looking for evidence of a particular disease such as cancer in persons with no symptoms of disease.

Sickle-cell anemia:

an inherited, potentially lethal disease in which a defect in hemoglobin, the oxygen-carrying pigment in the blood, causes distortion (sickling) and loss of red blood cells, producing damage to organs throughout the body.

Spina bifida:

is a fault in the spinal column in which one or more vertebrae (the bones which form the backbone) fail to form properly, leaving a gap or split.

Tay-Sachs disease:

an inherited disease of infancy characterized by profound mental retardation and early death; it is caused by a recessive gene mutation.

Thalassemia:

group of inherited conditions characterized by a reduced production of usual (or 'normal') hemoglobin. Hemoglobin is produced in the bone marrow and resides in the red blood cells and it carries the oxygen that is breathed into the lungs to different parts of the body.