Non-exhaustive list of definitions of terms used in gerontology and in senescence.info.
Aging: a progressive deterioration of physiological function, an intrinsic age-related process of loss of viability and increase in vulnerability. In humans, aging is characterized by a complex phenotype.
Allele: one of two or more variant forms of a gene.
Aphagy: inability to feed oneself due to anatomical deficiencies, common in the adult phase of some species of animals.
Apoptosis: programmed cell death.
Antagonistic pleiotropy: theory by George Williams that explains the existence of aging by the existence of genes beneficial early in life but harmful at later stages.
Autophagy: digestion of the cell's own components; it has been implicated in aging.
Biogerontology: the scientific study of the biological process of aging.
Caloric restriction (CR): diet regime consisting of eating considerably fewer calories that has been considered as a potential method to delay aging.
Cellular or clonal senescence: see replicative senescence.
Cellular immortality: the ability of certain cell populations, like most cancer cells, to divide indefinitely in culture.
Demography: the statistical study of populations; human aging is characterized by demographic aging.
Developmental theory of aging (DevAge): theory arguing that aging is an extension of developmental mechanisms.
Diphyodont: an animal that develops two successive sets of teeth, common in most mammals.
Diploid: a cell with two sets of chromosomes.
Dyskeratosis congenita: genetic disease caused by defects in the dyskerin protein, one of the components of telomerase.
Disposable soma theory: theory by Thomas Kirkwood that explains the existence of aging by the allocation of resources from somatic maintenance to reproduction.
Ectotherm: a cold-blooded animal, such as a reptile, fish, or amphibian, whose body temperature is mostly determined by the surrounding environment.
Endocrine system: group of hormone-producing glands and their secretions (hormones); the endocrine system have been implicated in aging.
Endotherm: a warm-blooded animal, like a bird and mammal, capable of regulating its internal temperature.
Epigenetics: study of heritable changes in a phenotype that are not due to alterations in the DNA sequence but rather due to chemical changes of the DNA and associated proteins.
Eutherian: a placental mammal. All mammals are eutherians with the exception of marsupials and monotremes.
Exonuclease: enzyme that cleaves nucleotides from one end of a strand of nucleic acid.
Free radical theory of aging: theory by Denham Harman that argues that aging is a result of damage accumulation caused by reactive oxygen species.
Gene: DNA sequence that encodes a protein and represents the basic unit of inheritance.
Genetics: the study of heredity--i.e., the passing of characteristics from one generation to another--and of variation of inherited characteristics. Aging has a strong genetic component.
Genomics: the study of an organism's genome.
Genome: the full DNA sequence of an organism.
Genotype: genetic makeup of a given organism, usually related to a given characteristic.
Geriatrics: the medical study of diseases and problems of the elderly.
Germ cells: the reproductive cells which contain the genetic material passed on to the offspring.
Gerontology: the scientific study of the aging process and old age. In the context of senescence.info, gerontology refers to the biological study of aging and old age, also called biogerontology.
Hayflick limit: the inability of cells to replicative indefinitely in culture.
Helicase: an enzyme that unwinds the DNA helix.
IMR: initial mortality rate. The age-independent mortality rate obtained from the Gompertz equation.
Iteroparous: an organism that may reproduce more than once during its lifespan.
Life expectancy: how long, on average, an animal can be expected to live. Can be used interchangeably with average lifespan and average longevity.
Life history: the changes organisms undergo from conception to death, focusing particularly on the schedule of reproduction and survival.
Lifespan: the period of time in which the life events of a species or sub-species (e.g., a strain or population) typically occur. Can sometimes be used interchangeably with longevity even though they have slightly different meanings.
Longevity: the period of time an organism is expected to live under ideal circumstances. Can sometimes be used interchangeably with lifespan even though they have slightly different meanings.
Maximum lifespan (tmax): the maximum period of time organisms of a given species or sub-species (e.g., a strain or population) can live. Usually refers to the longevity of the longest-lived individual of a given species or sub-species.
Mechanical senescence: age-related changes that are a consequence of mechanical usage.
Mitochondrion: cellular organelle that produces most of the cell's energy.
MRDT: mortality rate doubling time. The time required for the mortality rate to double. Inferred from the Gompertz equation.
Mutation: change in the DNA sequence of an organism or cell.
Mutation accumulation theory: theory by Peter Medawar that explains the existence of aging by the accumulation of mutations with harmful effects at later ages.
Negligible senescence: organisms in which the aging process has not been detected in spite of detailed studies, as observed in some animals.
Oocyte: a female gametocyte that develops into an ovum after two meiotic divisions.
Oogenesis: formation of new oocytes.
Oxidative stress: damage caused by reactive oxygen species; oxidative stress has been implicated in aging.
Phenotype: the characteristics of an organism as determined by both genetic makeup and environmental influences.
Phylogeny: the evolutionary development and history of a species or taxonomic group of species.
Polyphenism: the ability of a single genome to give rise to two or more morphologies.
Polyphyodont: an animal that develops several sets of teeth successively throughout its life, as observed in many species.
Polyploid: a cell with three or more sets of chromosomes.
Progeria: genetic disease resembling accelerated aging which typically affects children. Also called Hutchinson-Gilford syndrome.
Progeroid: a phenotype with features resembling accelerated aging.
Quiescent: in cell biology, a quiescent cell is one that is not dividing.
Rate of living theory: theory that argues that lifespan inversely correlates with metabolic rates.
Reactive oxygen species (ROS): any of a number of highly reactive forms of oxygen that are potential sources of damage; damage caused by ROS has been implicated in aging.
Replicative senescence: irreversible cessation of cell division of normally proliferating cells. It is also characterized by various biomarkers and can or not be accompanied by cell death.
Semelparous: organisms that reproduce only once, usually followed by death, as observed in several animals.
Senescence: the fundamental process of aging or aging itself. Can also refer to cellular aging in some contexts.
Senescent cell: normally dividing cell that is irreversibly growth arrested and exhibits a number of other biomarkers associated with cellular senescence.
Soma: the entire body of an organism with exception of the germ cells.
Stem cell: an undifferentiated cell that can divide, differentiate into specialized cells, and can self-renew to give rise to more stem cells.
Strategies for engineered negligible senescence (SENS): a proposal by Aubrey de Grey that details how by reversing seven forms of cellular and molecular age-related changes will allow us to cure aging.
Stress-induced premature senescence (SIPS): irreversible cell cycle arrest and associated cell phenotypes as the result of subcytotoxic stress.
Supercentenarian: someone 110 years of age or older.
Topoisomerase: an enzyme that regulate the supercoiling structure of the DNA.
Taxon (plural: taxa): a taxonomic group of any rank.
Telomeres: the long end sequences of a DNA strand occurring at the tip of the chromosomes that play a key role in replicative senescence.
Telomerase: enzyme that adds telomeric sequences to the telomeres and has been associated with cellular immortality.
Trait: a particular characteristic of an organism that can have different phenotypes.
Werner syndrome (WS): genetic disease resembling accelerated aging; it typically has an adult onset.
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