Terminology
Interested in exploring genetics even further? Here's help with some terms you may encounter along the way.
- Absolute risk
- Allele
- Allele frequency
- Association
- Base pair
- Case-control study
- Chromosome
- Citation
- Clinical trial
- Confidence interval
- CLIA
- DNA
- FDA
- Gene
- Genetics
- Genetic code
- Genetic marker
- Genetic screening
- Genetic sequencing
- Genome
- Genome-wide association study
- Genomics
- Genotype
- Genotype frequency
- Haplotype
- HapMap
- Heritability
- Incidence
- Absolute risk:
-
Your risk of developing a disease or health condition over a given time period.
- Allele (pronounced ah-LEEL):
-
An alternate form of a section of genetic code at a particular location on a chromosome. Different alleles may produce variation in inherited characteristics.
- Allele frequency:
-
How often an allele is observed in a population. This ranges from 0 to 100 percent.
- Association:
-
A statistically significant correlation between a health condition and a genetic marker or an environmental exposure.
- Base pair:
-
Two chemically bonded molecules that form a rung of the DNA ladder of "letters" of genetic code. In DNA, the code letters are A,T, G and C, which stand for the chemicals adenine, thymine, guanine and cytosine. In base pairing, adenine always pairs with thymine, and guanine always pairs with cytosine. The human genome has approximately 3 billion base pairs of DNA arranged into 23 chromosomes.
- Case-control study:
-
A study that compares a group of patient cases who have a particular health condition with a control group of patients that do not have that disease or exposure. This study design can produce an odds ratio but not a relative risk.
- Chromosome:
-
One of the threadlike "packages" of genes and other DNA in the nucleus of a cell. Humans have 23 pairs of chromosomes, 46 chromosomes in all. Each parent contributes one chromosome to each pair, so children get half their chromosomes from their mothers and half from their fathers.
- Citation:
-
A reference to a published scientific journal article.
- Clinical trial:
-
In medicine, a study comparing one group of patients against another, with different treatments or interventions, or possibly one group receiving no treatment or a placebo treatment. The pooled data is then statistically analyzed to determine the effects of treatment or intervention. The clinical trial is used to learn how better to manage patients, whether with treatments or in other ways.
- Confidence interval:
-
Used to determine the reliability of an estimated range of values by measuring the spread of data. The narrower the spread, the more confidence that the data is accurate.
- CLIA (Clinical Laboratory Improvement Amendments):
-
CLIA is a federal law that established quality standards for all laboratory testing to ensure the accuracy, reliability and timeliness of patient test results. Not all laboratories that perform genetic testing are CLIA-certified; the laboratory that Navigenics uses is.
- DNA (deoxyribonucleic acid):
-
The chemical inside the cell that carries the genetic instructions for making living organisms. DNA is made up of nucleotides, each of which has one of four types of molecules called bases. It is the sequence of these four bases along the backbone that encodes information.
- FDA:
-
Food and Drug Administration, the U.S. government agency that regulates pharmaceuticals and food.
- Gene:
-
Genes are segments of DNA dotted throughout the genome that contain blueprints for various proteins.
- Genetics:
-
A branch of biology that deals with the heredity and variation of organisms.
- Genetic code:
-
The chemical instructions in a gene that tell the cell how to make a specific protein. The letter codes A, T, G and C stand for the chemicals adenine, thymine, guanine and cytosine. Each gene's code combines these four chemicals in various ways to make a particular protein.
- Genetic risk marker:
-
A piece of DNA with an identifiable location on a chromosome whose inheritance can be traced and that can be associated with increased risk for a condition or trait.
- Genetic screening:
-
Testing a population group to identify a subset of individuals at high risk for possessing or transmitting a specific genetic disorder.
- Genetic sequencing:
-
Establishing all or part of a person's exact DNA sequence. A sequence captures every letter in the DNA, whereas a scan captures letters at precise locations.
- Genome:
-
The entire hereditary information of an organism, which is encoded in the DNA. This includes both genes and non-coding sequences of DNA.
- Genome-wide association study:
An approach that involves scanning genetic risk markers across the complete set of DNA, or genome, of many people to find genetic variations associated with a particular disease.
- Genomics:
The study of the global properties of genomes of humans and other organisms.
- Genotype:
An individual's genetic results at a particular location. At a marker with two alleles (for example, A and G) there are three possible genotypes, AA, AG or GG.
- Genotype frequency:
How often a genotype is observed in a population. This ranges from 0 to 100 percent.
- Haplotype:
A region of DNA that is usually inherited together.
- HapMap:
The International HapMap Project developed a map of the human genome, the HapMap, which describes the common patterns of human DNA sequence variation in four populations of the world (Chinese, Japanese, Yorubans and Utah residents of European ancestry.) "Hap" stands for "haplotype."
- Heritability:
Genetic heritability is determined by studies of twins. Values of less than 100 percent indicate that the environment or behavior also contributes to the condition or trait.
- Incidence:
The number of new cases of a disease in a population in a given time period.
- Lifetime risk:
The probability of having a health condition in your lifetime.
- Locus:
The location on a chromosome where a specific gene or marker resides. The plural is "loci," pronounced LOW-sigh.
- Non-risk allele:
-
The form of an allele that is not associated with increased risk for a condition.
- Nucleotide:
-
One of the building blocks of DNA. A nucleotide consists of a base (one of four chemicals: adenine, thymine, guanine or cytosine) plus a molecule of sugar and one of phosphoric acid.
- Odds ratio:
This shows how much your chances of developing a health condition are increased by your genotype. The higher it is, the greater the increase in your chances. The odds ratio is a way of comparing the odds of something happening to the odds of it not happening. (It is calculated differently from "relative risk.")
- Pharmacogenomics:
A field of medical genetics that analyzes the affect of personal genetic variation on a person's response to medications. Pharmacogenomic information can help doctors and patient make more personalized medication choices help determine a drug's effectiveness or reduce the risk of side effects.
- Phenotype:
The observable traits or characteristics of an organism, such as eye color or weight.
- Polymorphism:
A common variation in the sequence of DNA among individuals.
- Prevalence:
-
The total number of cases of disease in a population at a given time, or the total number of cases in the population divided by the number of individuals in the population.
- Proxy:
In terms of the Navigenics service, a proxy is a single nucleotide polymorphism (SNP) that serves as a reliable representative for another location or locations on the genome. Some locations on the genome can be difficult to access and analyze. In some such cases, a tag SNP may be easier to access for the purposes of obtaining a reliable genetic result. Such a proxy is often referred to by scientists as a "tag SNP."
- Published SNP:
-
This is the genetic marker that, in published research, was associated with increased risk of a condition.
- Reference population:
A sample population of individuals who provide a starting point for scientific research by allowing researchers to establish a norm. In genomics, reference populations are made up of people whose DNA sets the scientific standard for what is considered typical or distinctive for that group.
- Relative risk:
-
A statement of your risk relative to another person's risk. (It is calculated differently from the "odds ratio.")
- Risk allele:
-
The form of an allele that is associated with increased risk for a health condition.
- SNP (single nucleotide polymorphism, pronounced "snip"):
-
A common, one-letter variation in human DNA. A SNP is a site in the DNA where people differ in the base they have. For example, in a population, there might be either an A or a G at a particular location.
- Star allele:
A scientific way of naming particular genetic variants that are important in pharmacogenomics. Star allele namess are usually expressed in terms of a star symbol and a number (such as " *2 " or " *3 ") are pronounced using the term "star" and the number that follows (such as "star 2" or "star 3").
- Tag SNP:
A single nucleotide polymorphism (SNP) that serves as a reliable representative, or proxy, for another location or locations on the genome. Some locations on the genome can be difficult to access and analyze. In some such cases, a tag SNP may be easier to access for the purposes of obtaining a reliable genetic result.
- Test SNP:
-
This is the genetic marker we tested in your DNA. If not the same as the published SNP, it sits close to it on the chromosome and is known to be a good substitute.
- Whole-genome scan:
-
A method of scanning a person's entire genome, using microarrays or glass chips containing millions of short half-strands of DNA. In research, this procedure is used to find associations between genetic markers and diseases or traits; it can also be used (as Navigenics uses this technology) to see which genetic markers an individual carries.