Glossary of Genetic and Genomic Terms

Glossary of Genetic and Genomic Terms

• Allele: One of a series of alternative forms (genotypes) at a specific region (locus) of a chromosome.
• Autosome: A chromosome other than X or Y. Humans have 44 autosomes (22 pairs).
• Carrier: A person heterozygous for a gene variant that causes autosomal recessive or X-linked recessive disease. Used to describe heterozygotes for risk alleles of complex traits with variable penetrance
• Carrier rate: Frequency of carriers in a population.
• Carrier testing: Clinical method to identify at-risk family members of populations who are usually asymptomatic but may have a pathogenic variant.
• Chromosome: Microscopic structures in the cell nucleus comprised of chromatin, containing genetic information. Humans typically have 46 chromosomes (23 pairs).
• Codominance: Expression of each pair of alleles when present in the heterozygous state (e.g., AB blood type).
• Congenital: Present at birth.
• Consanguineous: Reproduction between 2 persons from the same bloodline, such as first or second cousins. Increasing probability of rare recessive diseases.
• Dominant allele: Gene expressed in the phenotype of a heterozygous person
• Familial disorder: A trait that appears with higher frequency among close relatives than in the general population.
• Gene: Functional unit of heredity, a unit of DNA sequence that encodes for a specific functional product, such as RNA.
• Genetic risk: Probability that a trait will occur or recur in a family, based on the knowledge of its genetic pattern of transmission.
• Genetics: Study of genes and their role in inheritance.
• Genome: All the DNA contained in a person, which is the person's genetic constitution.
• Genome-wide association study (GWAS): A type of genetic mapping study that scans complete DNA sets of many people to find genetic variations associated with particular diseases.
• Genomics: Study of how genes interact and influence people's biological and physical characteristics.
• Genotype: Genetic identity of a person.
• Haploid: Cells or organisms possessing one copy of each autosomal chromosome and one copy of each sex chromosome (e.g. ova and sperm).
• Hereditary: Transmission of a disease, condition, or trait from parent to children.
• Heterozygous: Having two different alleles for one given gene, one inherited from each parent.
• Homozygous: Having two identical alleles for one given gene, one inherited from each parent.
• Locus: Position of a gene on a chromosome.
• Mutation: A change in a gene that affects function (e.g., nonsense, missense, silent, frameshift). A mutation associated with a disease is called a pathogenic variant.
• Oncogene: A gene that contributes to the conversion of normal cells into cancer cells (usually dominant).
• Pedigree: A graphic representation that shows family relationships, gender, age, and presence of diseases for each family member.
• Pharmacogenetics: Study of variability of drug metabolism related to variations in single genes.
• Pharmacogenomics: Study of variability of drug metabolism in relation to variations in and interactions of multiple genes or the person's genome.
• Phenotype: Observable characteristics of a person (measurable categorically or quantitatively).
• Protooncogene: Genes that can be turned into oncogenes (an oncogene that synthesises structurally altered proteins) by a dominant activating mutation.
• Recessive allele: Allele with no noticeable effect on the phenotype in a heterozygous person
• Trait: Physical characteristic that one inherits (e.g, hair or eye color)
• X-linked gene: Gene found on the X chromosome rather than an autosome. Sex-linked disorders are often seen in males.