Glossary
Amniocentesis
A procedure in which a small amount of amniotic fluid is removed through a needle from the fetal sac at about 16 weeks pregnancy. The fluid is studied for chromosomal abnormalities that may affect fetal development.
Aneuploidy
A chromosome abnormality in the number of chromosomes. Typically there are pairs (2) of chromosomes. A change to this number (more or less) often results in a miscarriage or genetic disorder to the child. For example, trisomy 21 (three chromosome 21s) causes Down’s syndrome.
Antibody
A Y-shaped protein, naturally in blood, used by the immune system. It is specific for binding (like a perfect puzzle piece) to another substance (see “antigen”). Antibodies are made when the body detects something foreign to destroy (ie. bacteria, viruses). They can also play a role in the lab for detection assays.
Antigen
Something foreign or toxic detected by the body. The body creates proteins that will bind to these to flag it to be destroyed (see “antibody”).
Array-Comparative Genomic Hybridization (aCGH)
CGH is is a method for analyzing regions of chromosomes to determine aberrations in the number of copies, by comparing to a control reference. When an array is used (aCGH), it can detect smaller differences and is therefore more specific. aCGH was originally used for Preimplantation Genetic Screening/Diagnosis (PGS/PGD, now PGT-A/PGT) by MSS. See “chromosomes” and “microarray”.
Assay
A laboratory term for a test.
Biomarker
A naturally occurring and measurable characteristic/molecule/gene that may indicate a specific process in the body, such as a disease.
Biopsy
A sample (tissue/cells) removed from a living body for analysis (often to look for a disease).
Blastocyst
A structure formed early in the development of mammals (~day 5), made up of a few hundred cells. Cells may be taken (biopsied) from this for PGS/PGD.
Cancer
A collection of diseases that involve abnormal growth of cells. Genes are mutated or "turned on" to keep the cell growing. This has potential to spread to other areas of the body.
Cell-free DNA (cfDNA)
Fetal DNA that circulates in the mother’s bloodstream and is not within a cell. This is used by the NIPT to look for chromosome abnormalities of the fetus.
Chorionic villus sampling
A procedure in which a small sample of cells is taken from the placenta early in a pregnancy for chromosome testing.
Chromosomes
Rod-shaped structures located in the nucleus of a cell which contain hereditary (genetic) material. The rod is made up of a short (p) and long (q) arm. Humans have 23 pairs of chromosomes (46 in total, 23 from each parent). Two of the 46 are the sex chromosomes, which are X and Y chromosomes. Biological females have two X chromosomes and biologic males have one X and one Y chromosome.
Clinical trial
A regulated stage of development of a new drug by testing it in humans. The purpose is to see if the drug works well (is effective) and is safe.
Consent
Giving permission for your involvement and that you understand what is involved (e.g. consent to participate in a research study). Typically this involves signing a form (providing written consent).
Contract Research Organization (CRO)
An organization that provides outsourced research services to biotechnology, pharmaceutical, and medical device/diagnostic industries on a contract basis. MSS provides CRO services and also works to support other CROs.
Diabetes
A chronic, genetic (Type I) or developed (Type II or Gestational), condition that affects the body’s ability to either produce or use insulin (a hormone for regulating sugar levels in the blood).
Diagnostic
Related to the identification of a disease or condition. For example, a molecular diagnostic test for hereditary breast cancer is a test that examines changes in the DNA sequence in a breast cancer patient (compared to a healthy individual) to determine/diagnose if their breast cancer is inherited, and may be passed on to their offspring. MSS works with some companies that are developing medical diagnostic tests. Please also see “Screening”.
DNA
Deoxyribonucleic acid (DNA) is the genetic instructions of everything living. The code/sequence of the DNA is made up of two types of paired molecules called bases: C+G or A+T. The DNA takes on a ladder-type structure, where the paired bases are the rungs. DNA is packaged into “chromosomes” and stored in the nucleus of cells.
Embryo
Earliest stage of human development after sperm fertilizes an egg.
Failure rate
How often a test fails (due to technical failure). When a test fails, a result may not be produced—a sample may need to be collected and the test repeated.
Gene
A hereditary unit/sequence of DNA on a chromosome that defines a characteristic.
Genetic
Referring to inherited conditions, usually due to genes located on the chromosome.
Genetic counsellor
A healthcare professional who has a Masters of Science in Medical Genetics/Genetic Counselling. They provide information, support, and suggest options to prospective parents who may be concerned about risks of passing on genetic conditions.
Inflammatory Bowel Disease (IBD)
A chronic condition of inflammation to the digestive tract. Major types of IBD include ulcerative colitis (limited to the large intestine) and Crohn’s disease.
Intracytoplasmic sperm injection (ICSI)
A method of assisted reproduction that involves the direct injection of a sperm into an egg to fertilize it in the laboratory. It is then transferred into the uterus to hopefully implant and further develop.
In vitro fertilization (IVF)
A method of assisted reproduction that involves combining an egg with sperm in a laboratory dish. If the egg is fertilized and begins cell division (now an “embryo”), it is transferred into the uterus to hopefully implant and further develop.
Karyotype
A test that looks at the size, shape, and number of chromosomes.
Key opinion leaders (KOLs)
Recognized physicians who have a large influence on medical practice and behaviours.
KRAS
A gene that is found to be mutated in approximately 30-50% of colorectal tumours. Patients with specific KRAS mutations typically respond favourably to targeted therapies. See “proto-oncogene”, “mutation”.
Microarray
A set of DNA sequences arranged in a grid pattern, used for genetic testing.
Microdeletion
A small deletion of genetic material. Specific deletions that include coding regions of chromosomes (i.e. genes) may cause diseases. For example, the most common microdeletion is known as 22q11.2 and causes DiGeorge syndrome. The notation represents that the deletion is at a location designated as 11.2 on the q (long) arm of chromosome 22. See “chromosomes”.
Mosaic/Mosaicism
Two or more populations of cells with different genetic makeups (chromosomes are not identical), within one individual.
Mutation (Variant)
A change in the genetic code (DNA sequence). Although the term "mutation" is widely understood, the preferred term among the scientific and medical community is "variant"; not all changes in the DNA sequence cause disease, and "mutation" is often synonymous with disease-causing variants (i.e. pathogenic variants). These can be inherited or caused by the environment (radiation, chemicals). Some variants at the DNA-level do not result in a change at the protein-level ('silent variants'), but some may cause a change in the protein and lead to diseases, such as cancer (see “proto-oncogene”).
Negative predictive value (NPV)
The probability that subjects with a negative screening test result will not have the condition. See “Positive predictive value (PPV)”.
Next-Generation Sequencing (NGS)
A new and faster technology to sequence DNA or RNA.
Noninvasive Prenatal Testing (NIPT)
A screening test that is used to look for chromosome abnormalities (aneuploidies and some microdeletions) as early as 10 weeks pregnancy. This requires a simple blood draw, and looks at fetal cell-free DNA in the mother’s blood. Note that for a diagnosis of a genetic condition more invasive methods (amniocentesis and chorionic villus sampling) are required.
Oncogene
A gene, typically involved in cell growth, that is aberrantly overexpressed and dysregulated causing tumour growth. See “proto-oncogene”.
Personalized medicine
A term that was intended to describe a medical treatment that would be selected for an individual based on their genetic code. However, the use of “personalized” in this term is misleading, as the treatment is not created specifically for the person; an existing treatment is tailored to patients with certain genetic variants. See “precision medicine”.
Pharmacogenetics
The study of how drugs (pharmaceuticals) work differently (their effect and how long they last) in individuals based on variations in genes involved in drug metabolism.
Precision medicine
An approach for treating and preventing diseases that accounts for an individual's genetic variations, environment and lifestyle.
Preimplantation Genetic Testing for Aneuploidy (PGT-A) or diagnosis (PGT)
A test that looks for chromosome abnormalities in embryos before transfer into the uterus after methods such as IVF. See "aneuploidy".
PGT-A and PGT were previously known as Preimplantation Genetic Screening (PGS) and Diagnosis (PGD), respectively.
Positive predictive value (PPV)
This calculated value is reported on some test results, noting the probability that the subject with the positive test result truly has the condition. It takes factors about the subject into consideration; for example, it considers age for NIPT.
Proto-oncogene
A gene that, if mutated, will become an oncogene due to overexpression. See “oncogene”.
Recessive
A genetic characteristic that must be inherited from both parents to be expressed.
Requisition
An order for a test to be done (usually must be from a doctor). This is often as a form that must be completed and brought with you when you go for a blood draw or testing.
Screening
Evaluation to assess. A positive screening test does not confirm the condition. For example, NIPT is a screening test, but other methods (“Amniocentesis” or “Chorionic Villus Sampling”) are used to confirm/diagnose (see “Diagnostic”).
Sensitivity
The proportion of patients with the condition that will test positive for the condition (true positive). Also see “specificity”.
Sequencing
The process of determining the genetic code (sequence) of DNA. The code is made up of the bases, C, G, A, or T.
Specificity
The proportion of patients without the condition that will test negative for the condition (true negative). Also see “sensitivity”.
Translocation
The rearrangement of a part of a chromosome with a different one. This may be balanced (an even exchange in that no genetic material is missing), or unbalanced (genetic material is unequal, being extra or missing genes).
X-linked
A genetic trait that is on the X chromosome.