15) Glossary

Here are some terms related to genetic testing that may be helpful!

A

Absolute risk: In terms of health conditions, the prevalence of a disease within an entire population (e.g., 3% of all people will get Disease X in their lifetime).

Actin: A protein within muscle tissue.

Adenine: One of the nucleotides that forms DNA / RNA, along with cytosine, guanine, and thymine (uracil in RNA). Often abbreviated as A. In base pairing, adenine pairs with thymine (T) and uracil (U).

Adipocyte: A fat cell.

Allele: A variant of the same gene with small differences in their sequence of DNA bases (usually emerging through mutation), found at the same place on the chromosome. The different base pairs at a SNP

Allergy: A hypersensitive immune system response. 

Amino acid: The basic building block for a protein.

B

Bioactive form: A form of a molecule or compound that has an effect on a biological organism (e.g., “Before we can absorb Substance X, it must be converted into its bioactive form”).

Body composition: The relative amount of fat mass to lean mass.

Body mass index (BMI): A measure of weight relative to height.

 C

Carbohydrate: A family of biological molecules that includes sugars, starches, and soluble and insoluble fiber.

Celiac disease: An autoimmune disorder in which the body makes antibodies to gluten, causing damage to the gastrointestinal lining.

Cell: The basic building blocks of all living things. They provide structure, take in nutrients, convert nutrients into energy and contain the hereditary material, DNA.

Cholesterol: A waxy lipid that we can make in our liver or consume from food. We use cholesterol to make many important molecules that our bodies use, including our sex hormones.

Chromosome: A long strand of tightly wound chromatin that contains genetic information. Humans have 23 pairs of chromosomes.

Clinical Laboratory Improvement Amendments (CLIA) regulations: A set of federal standards applicable to all US facilities or sites that test human specimens for health assessment or to diagnose, prevent, or treat disease.

Codon: A set of three nucleotides that codes for a specific protein.

Complex traits: Traits that are a result of the combination of many genes as well as changes in gene expression and environmental factors.

Copy number variation (CNV): Repetition of specific sections of genetic material; the number of repetitions can vary from person to person.

Cytosine: One of the nucleotides that forms DNA / RNA, along with adenine, guanine, and thymine (uracil in RNA). Often abbreviated as C. In base pairing, cytosine pairs with guanine (G).

D

Deletion: A mutation in which some genetic material is lost during the process of DNA replication.

Deoxyribose: The sugar-based structural “backbone” of DNA.

DNA: A biological molecule that holds the code for making all living things.

Dominant traits / genes: Traits and/or genes that are more likely to be expressed, and which require only one copy to do so.

E

Epigenetics: The study of factors that affect genetic expression — for instance, how the same genetic “blueprint” may actually be used to build different things.

Environmental factor: A factor that influences the development of a phenotype, disease or condition. This can include both the external environment (education, climate, exposure to toxins, lifestyle etc.) and internal environment (metabolic factors, hormones, oxidative stress etc.). 

Environmental risk factor: When an environmental factor increases disease risk but does not directly cause a disease.

Enzyme: A substance that helps initiate a particular biochemical reaction, often breaking things down (e.g. protease enzymes break down proteins).

Exon: The parts of the gene that code for protein sequences (the opposite of introns).

Exome: The part of the gene formed by exons.

G

Gametes: A haploid germ cell of sexual reproduction (i.e., egg/ovum or sperm).

Genes: Regions of DNA that have instructions for making specific proteins. 

Genetic discrimination: When an employer or insurance company uses the results of a person’s genetic test to make decisions about employment, coverage or benefits.

Genetic factor: A genetic variation that plays a role in increasing or decreasing a person’s risk of developing a phenotype, disease or condition. When a genetic factor increases disease risk but does not directly cause a disease, it is called a genetic risk factor. 

Genetic test: A laboratory assay that is used to identify specific genotype(s) to diagnose a specific disease or condition.

Genetic variations: The presence of differences in DNA sequences between individuals of the same species. It enables natural selection, one of the primary forces driving the evolution of life.

Genetics: The study of genes, how they work, and how particular traits (such as eye color) are passed from parent to offspring (known as heredity).

Genome: An organism’s total set of genetic material.

Genome-wide association studies (GWAS): A type of genetic test that examines locations across the entire genome to identify potential associations with a particular phenotype or phenotypes.

Genotype: The genetic code of an organism.

Glucose: A simple sugar that is the raw material for building ATP, our cells’ energy.

Glutamine: An amino acid.

Gluten: A protein found in wheat to which some people (such as those with celiac disease) have an immune system reaction.

Guanine: One of the nucleotides that forms DNA / RNA, along with adenine, cytosine, and thymine (uracil in RNA). Often abbreviated as G. In base pairing, guanine pairs with cytosine (C).

H

Heredity: The transmission of particular characteristics from one generation to another.

Heritability: The degree of genetic variation between people on a trait. The proportion of an observed variation in a particular trait that can be attributed to inherited genetic factors in contrast to environmental ones. Or, the extent to which genetic differences contribute to differences in the observed behaviour.

Histamine: A substance released by cells in allergic and inflammatory reactions (and injury), which causes contraction of smooth muscle and dilation of blood vessels.

Histones: A type of protein found in chromatin, which acts like a “spool” or “bead” around which the strings of DNA are wound. Because of this structure, they can affect genetic expression.

Histone modification: Changes to histones (such as acetylation or various types of methylation) after RNA translation that can affect genetic expression.

I

Inflammation: A complex and coordinated process of response to injury and illness that is characterized by elevated inflammatory chemicals (such as interleukins) and pain, heat, redness and swelling.

Insulin: A crucial hormone for nutrient storage and anabolism that is released by the pancreas in response to higher blood sugar (glucose) levels.

Insulin resistance: A condition in which our cells cannot respond appropriately to the presence of insulin by transporting glucose into cells. As a result, we have high circulating insulin and high circulating glucose. This is often a precursor to Type 2 diabetes.

Insulin sensitivity: How able our cells are to respond appropriately to insulin. We want this to be working well, and to have high insulin sensitivity. If we have poor sensitivity, we develop insulin resistance.

Intron: A part of the gene or gene transcript that is removed before the mature RNA is translated to a protein (the opposite of exons).

L

Lactase: An enzyme that allows us to digest lactose, a sugar in milk.

Lactase persistence: Presence within a population of the ability to digest lactase as an adult, which is largely genetically determined. Lactose tolerance: The ability to digest lactase.

Lipolysis: The breakdown of fats (lipids).

Lipoproteins: Proteins that transport lipids. Since lipids can’t dissolve in water but proteins can, lipoproteins help many fat-based molecules move around the body through the blood.

Locus (plural: loci): A position of genetic material on a chromosome that describes exactly where that genetic material is located.

 M

Metabolic syndrome: A collection of physical risk factors that are related to a cluster of chronic diseases, such as Type 2 diabetes and stroke. These include elevated blood pressure, elevated triglycerides, high fasting blood sugar, and significant deposits of fat around the midsection and internal organs.

Methylation: The addition of a methyl group (a carbon and 3 hydrogens, aka CH3) to a molecule. Two important processes in epigenetics are the methylation of bases in DNA (usually cytosine, or C) and the methylation of histone proteins that affect gene expression. When DNA or histones are methylated, certain genes are often “switched off”, which can be a problem if you want those genes to be transcribed and protein made.

Microarray: A chip with a large array of sensors to detect certain DNA or RNA sequences.

Mitochondria: An organelle within a cell that’s involved in energy production and respiration.

Mitochondrial DNA (mtDNA): A form of non-nuclear DNA that is round in humans and transmitted maternally. We can use mtDNA to trace maternal ancestry.

Mitosis: Division of one cell into two genetically identical cells.

Mutation: A permanent alteration in the DNA sequence that makes up a gene, such that the sequence differs from what is found in most people. Changing the structure or function of a gene in a way that can potentially be transmitted to future offspring.

N

Natural selection: The process through which populations adapt and change over time. Individuals in a population are naturally variable, meaning that they are all different in some ways. Individuals better adapted to their environment tend to survive and produce more offspring. Because the environment is constantly changing, no organism is perfectly adapted to its environment. Thus, natural selection is constantly influencing the evolution of species.

Non-celiac gluten sensitivity (NCGS): An inflammatory response to gluten that does not depend on making IgG antibodies, as in celiac disease.

Noncoding regions / noncoding DNA: Parts of the genetic code that don’t code for any proteins, but that might be involved in other genetic regulatory and structural functions.

Nucleotide: The basic structural unit of DNA and RNA; a nitrogen-containing base plus a phosphate and sugar molecule (such as deoxyribose or ribose).

Nucleus: An organelle within a cell where genetic material is stored (in eukaryotes).

O

Odds ratio:  measure of association between an exposure and an outcome.

P

p-value: Calculates the probability of observing the data (an association) if the null hypothesis (no association) were true.

Phenotype: The combination of traits and features that results after an organism’s genetic code interacts with its environment; how a genetic “blueprint” is actually expressed. Usually relating to the characteristics of an individual. These characteristics can include physical form, developmental processes, biochemical and physiological properties, behavior, and the products of behavior.

Polygenic: Many genes involved (e.g., in the cause or progression of a disease).

Polymerase chain reaction process (PCR): A laboratory technique used to make multiple copies of a specific region of DNA, for instance for genetic testing.

Polymorphism: Genetic alterations that occur in more than 1 percent of the population are called polymorphisms. Polymorphisms are common enough to be considered a normal variation in the DNA. Multiple forms or variants of a gene at the same location. 

Positive selection: a genetic mutation that promotes the emergence of new phenotypes, usually by offering some kind of advantage.

Primary lactose intolerance: Is common and involves reduced lactase production with age. 

Predictive value: How well a given factor, such as a genetic variant (or set of variants), can explain an outcome, such as a disease or trait.

Protein: A biological molecule, made of amino acids, that a gene codes for.

R

Reactive oxygen species: Waste products generated from the normal process of cellular metabolism, which contain oxygen and are chemically reactive.

Receptor: A structure that is able to respond to and bind specifically with something else, such as a molecule.

Recessive traits / genes: Traits that require two gene copies — one from each parent, to express that trait.

Reference genomes: A database of a “representative” genome of a species, used as an example or relative comparator for other genomes of the same species.

Relative risk: The risk of a given outcome as compared to another person or group (e.g., Disease X occurs 2 times more in Group Y than Group Z).

S

Secondary lactose intolerance: Is caused by inflammation in the gut, secondary to an infection or disease.

Single nucleotide polymorphism (SNP): A variation in a single nucleotide (for instance, having a cytosine, or C, where there’s normally an adenine, or A).

SNP genotyping arrays: Arrays that look at a series of predetermined locations on the genome (usually hundreds of thousands to millions) to look for SNP variations.

T

Thymine: One of the nucleotides that forms DNA, along with adenine, cytosine, and guanine. Often abbreviated as T. In base pairing, thymine pairs with adenine (A). In RNA, thymine is replaced by uracil (U).

Trait: A particular characteristic of an organism (such as eye color or hair texture) that is expressed by gene(s) as well as influenced by the environment.

Transcription: The process of copying a segment of DNA into RNA.

Translation: The process of synthesizing proteins from RNA.

Triglyceride: The storage and transport form of fatty acids, formed with three fatty acids attached to a glycerol “backbone”.

Type 1 diabetes (T1D): Often called early-onset diabetes, an autoimmune disorder where destruction of the pancreas leads to problems with insulin secretion.

Type 2 diabetes (T2D): A disease in which the body cannot use insulin properly, and blood glucose (sugar) remains consistently high.

V

Variant: A different version of the same gene. The genetic variations or differences that make up the 0.5% to make each person unique. See also allele. 

W

Whole-genome sequencing: “Reading” and analyzing an organism’s entire genome.