Genetic Glossary | EasyDNA South Africa

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

A
Acrochordon A small, benign skin growth that may have a stalk (peduncle). Acrochordons most commonly appear on the neck, axillary, groin, and inframammary regions. Also called skin tag.
ALL (Acute Lymphoblastic Leukemia) A cancer of lymphocytes (the white blood cells) characterized by excess lymphoblasts. When the disease is malignant, immature lymphocytes continuously multiply and are overproduced in the bone marrow, causing normal cells to be outnumbered in this region.
AML (Acute Myeloid Leukemia) A cancer of the myeloid line of blood cells, characterized by rapid growth of white blood cells accumulating in bone marrow and interfering with the production of normal blood cells in bone marrow.
Anti-oncogene A type of gene that regulates cell growth. When an antioncogene is mutated, uncontrolled cell growth may occur.
Autosome All chromosomes, excluding sex chromosomes are classified as autosomes. Humans have a total of 22 pairs of autosomes.
Autosomal dominant Autosomal dominant inheritance refers to genetic conditions that occur when a mutation is present in one copy of a given gene .
Autosomal recessive Autosomal recessive inheritance refers to genetic conditions that occur only when mutations are present in both copies of a given gene.
 B
Benign Tumor A non-malignant tumor that remains localized and does not spread to other sites; generally amenable to local surgical removal and survival of the patient.
C
Carcinoma Malignant growth of epithelial cells.
Carrier Clinically an individual who carries a deleterious allele that predisposes to disease.
Chromosome Discrete physical structures inside a cell nucleus that consist of proteins and DNA organized into genes.
CLL (Chronic Lymphocytic Leukemia) A cancer of white blood cells, in which mature lymphocytes function abnormally and cause disease.
CML (Chronic Myeloid Leukemia) Cancer of the white blood cells in which rapid growth of white blood cells (WBC’s) leads to chronic leukemia, one subtype being chronic lymphoblastic leukemia (CLL) and the other being chronic myeloid leukemia (CML) affecting abnormal proliferation of WBC’s called granulocyte
Consanguinity Genetic relatedness between individuals who are descendants of at least one common ancestor.
Cutaneous leiomyoma A benign tumor that arises from smooth muscle tissue in a hair follicle, forming a papule. Cutaneous leiomyomas (or leiomyomata) can be painful in the presence of cold or tactile stimuli.
Cytogenetics The study of the structure, function, and abnormalities of human chromosomes.
D
Deleterious mutation A genetic alteration that increases an individual’s susceptibility or predisposition to a certain disease or disorder.
DNA (Deoxyribonucleic Acid) Long double-stranded molecule found in the nucleus of cells and packaged into chromosomes. DNA contains the genetic instructions used in the development and functioning of organisms.
Duplication Phenomena resulting in an extra (abnormal) copy of a genomic duplicated material.
E
Epigenetics The study of heritable changes that do not affect the DNA sequence but influence gene expression.
Exon The sequence of DNA present in mature messenger RNA, some of which encodes the amino acids of a protein.
F
Familial A phenotype or trait that occurs with greater frequency in a given family than in the general population.
First-degree relative The parents, siblings, or children of an individual. Also called FDR.
FISH (Fluorescence in situ hybridization) Fluorescence in situ hybridization (FISH) is a molecular cytogenetic technique that permits physical visualization and mapping of specific genes or loci
G
Gene The basic unit of heredity that occupies a specific location on a chromosome. Each consists of nucleotides arranged in a linear manner. Most genes code for a specific protein or segment of protein leading to a particular characteristic or function.
Genome Refers to the total genetic material in the chromosomes from a cell of an organism.
Genetic Disorder Disease resulting from the alteration of the genome of an individual. The genetic abnormality can caused by small mutation in a single gene by the addition or deletion of an entire chromosome or set of chromosome
Genetic counseling A communication process that seeks to assist affected or at-risk individuals and families in understanding the natural history, disease risks, and mode of transmission of a genetic disorder; to facilitate informed consent for genetic testing when appropriate; to discuss options for risk management and family planning; and to provide for or refer individuals for psychosocial support as needed.
Genetic predisposition Increased likelihood or chance of developing a particular disease due to the presence of one or more gene mutations and/or a family history that indicates an increased risk of the disease.
Genetic screening Genetic testing designed to identify individuals in a given population who are at higher risk of having or developing a particular disorder, or carrying a gene for a particular disorder.
H
Heritability The proportion of variation in a population trait that can be attributed to inherited genetic factors.
Histopathology Refers to the examination of a tissue specimen under a microscope in order to detect the manifestation of a disease.
Hodgkin’s Lymphoma A rare lymphoma or cancer of the lymphatic system, originating from white blood cells (lymphocytes).
Homologous Chromosomes A pair of chromosomes of the same length, centromere position and staining pattern, and shape. Each chromosome in a pair is inherited from each parent.
I
Informed consent Permission granted in full knowledge of the possible consequences, typically that which is given by a patient to a doctor for treatment with knowledge of the possible risks and benefits. A process of information exchange between a clinician and an individual or their legal proxy designed to facilitate autonomous, informed decision making.
Inherited cancer syndrome Describes the clinical manifestations associated with a mutation conferring cancer susceptibility.
K
Karyotype The arrangement of the chromosomes of a single cell in the standard classification of descending size, appropriate centromere location and banding pattern. A normal Karyotype includes 22 pairs of autosomes and one pair of heterochromosomes (XX or XY)
Kindred An extended family.
L
Leukemia Any of several acute or chronic forms of neoplastic disease of the bone marrow in which unrestrained proliferation of white blood cells occurs.
Locus The physical site or location of a specific gene on a chromosome.
Lymphoma Cancer affecting the lymphatic system, usually lymphocytic, including the spleen and lymph nodes. Lymphomas are divided into Hodgkin’s disease or Non-Hodgkin’s Lymphoma.
M
Malignant Tumor A tumor with properties of invasion and metastasis which can cause death.
Mode of inheritance The manner in which a genetic trait or disorder is passed from one generation to the next.
Multigene test Genetic tests that use next-generation sequencing to test multiple genes simultaneously. Also called multiple-gene panel test and multiple-gene test.
Mutation A change in the usual DNA sequence at a particular gene locus. The term variant is sometimes used as a synonym for the term mutation.
Myeloid Cells White blood cells, specifically granulocytes and monocytes.
N
Next-generation sequencing A high-throughput method used to determine a portion of the nucleotide sequence of an individual’s genome. This technique utilizes DNA sequencing technologies that are capable of processing multiple DNA sequences in parallel.
NHL (Non-Hodgkin’s Disease) A cancer of lymphocytes that spreads more easily to other parts of the body.
Nonsense mutation A genetic alteration that causes the premature termination of a protein.
Novel mutation A newly discovered, distinct genetic alteration.
Nucleotide A molecule consisting of a nitrogen-containing base (adenine, guanine, thymine, or cytosine in DNA; adenine, guanine, uracil, or cytosine in RNA), a phosphate group, and a sugar (deoxyribose in DNA; ribose in RNA).
O
Oncogene A dominant-acting gene that has transforming ability, (i.e., causing a cell to grow in an uncontrolled manner) and is responsible for tumor development.
P  
Pathogenic variant A genetic alteration that increases an individual’s susceptibility or predisposition to a certain disease or disorder. When such a variant (or mutation) is inherited, development of symptoms is more likely, but not certain. Also called deleterious mutation, disease-causing mutation, predisposing mutation, and susceptibility gene.
Pedigree A graphic illustration of family history.
Penetrance A characteristic of a genotype; it refers to the likelihood that a clinical condition will occur when a particular genotype is present.
Phenotype The observable characteristics in an individual resulting from the expression of genes; the clinical presentation of an individual with a particular genotype.
Point mutation A genetic alteration caused by the substitution of a single nucleotide for another nucleotide. Also called point variant.
Polymorphism The presence of genetic variation within a population, upon which natural selection can operate.
Probe A small segment of DNA of known origin, designed to recognize complementary DNA on specific parts of chromosomes (targets).
Proto-oncogene A normal gene that can become an oncogene due to mutations or increased expression. The resultant protein may be termed an oncoprotein.
R
Recurrence risk In genetics, the likelihood that a hereditary trait or disorder present in one family member will occur again in other family members.
Relapsed Diseases Incomplete response to treatment of cancers, resulting in a recurrence of the disease.
Repetitive DNA DNA sequences that are present in multiple copies in the genome.
S
Single nucleotide polymorphism DNA sequence variations that occur when a single nucleotide (adenine, thymine, cytosine, or guanine) in the genome sequence is altered; usually present in at least 1% of the population. Also called SNP.
Somatic variant An alteration in DNA that occurs after conception and is not present within the germline. Somatic variants can occur in any of the cells of the body except the germ cells (sperm and egg) and therefore are not passed on to children. Somatic variants can (but do not always) cause cancer or other diseases.
Sporadic cancer Cancer developing in people who do not carry a high-risk mutation is referred to as sporadic cancer. Alternatively, sporadic is also sometimes used to describe cancer occurring in individuals without a family history of cancer.
Surveillance Periodic clinical evaluation of an individual who is at increased risk of developing a condition aimed at detecting new or recurrent disease.
Susceptibility gene A genetic alteration that increases an individual’s susceptibility or predisposition to a certain disease or disorder.
T
Trichilemmoma A benign tumor arising from the outer cells of the hair follicle.
Triple-negative breast cancer Triple-negative breast cancer is defined by a lack of expression of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2/neu). Also called ER-negative PR-negative HER2/neu-negative breast cancer.
Trisomy The presence of an extra chromosome, resulting in a total of three copies of that chromosome instead of the normal 2 copies.
Tumor sequencing Sequencing of somatic tissue, such as tumors, refers to looking for variants in DNA that typically occur after conception. Somatic mutations can occur in any of the cells of the body except the germ cells (sperm and egg) and therefore are not passed on to children.
Tumor suppressor gene A type of gene that regulates cell growth. When a tumor suppressor gene is mutated, uncontrolled cell growth may occur. This may contribute to the development of cancer. Also called antioncogene.
V
Variable expression Variation in the manner in which a trait is manifested. When there is variable expressivity, the trait may vary in clinical expression from mild to severe.
Variant of uncertain significance A variation in a genetic sequence whose association with disease risk is unknown.
Variant of unknown significance A variation in a genetic sequence whose association with disease risk is unknown.
W
Whole-exome sequencing A laboratory process that is used to determine the nucleotide sequence primarily of the exonic (or protein-coding) regions of an individual’s genome and related sequences, representing approximately 1% of the complete DNA sequence.
Whole-genome sequencing A laboratory process that is used to determine nearly all of the approximately 3 billion nucleotides of an individual’s complete DNA sequence, including non-coding sequence.
X
X-linked dominant X-linked dominant inheritance refers to genetic conditions associated with mutations in genes on the X chromosome. A single copy of the mutation is enough to cause the disease in both males (who have one X chromosome) and females (who have two X chromosomes.
X-linked recessive X-linked recessive inheritance refers to genetic conditions associated with mutations in genes on the X chromosome. A male carrying such a mutation will be affected, because he carries only one X chromosome. A female carrying a mutation in one gene, with a normal gene on the other X chromosome, is generally unaffected.
x

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