lipofectionDelivery into eukaryotic cells of DNA, RNA or other compounds that have been encapsulated in liposomes.
lipopolysaccharide(Abbreviation: LPS). A compound containing lipid bound to a polysaccharide; often a component of microbial cells walls.
liposome(LY-puh-some) A very tiny, fat-like particle that is made in the laboratory. In medicine, liposomes containing drugs or other substances are used in the…
LiposomesMembrane-bound vesicles constructed in the laboratory to transport biological molecules.
LiquefactionEnzymatic digestion (often by alpha-amylase) of gelatinized starch to form lower molecular weight polysaccharides.
liquid mediumCulture solution, without a solidifying agent, for in vitro cell growth.
liquid membraneThin films made up of liquids (as opposed to solids) which are stable in another liquid (usually water).
liquid nitrogenNitrogen gas condensed to a liquid with a boiling point of about -196 °C. Commonly used as a medium for long-term storage of biological materials.
litmus paperA pH indicator paper. It turns red in acidic and blue in alkaline solutions.
live recombinant vaccineA vaccine created by the expression of a pathogen antigen in a non-pathogenic organism.
live vaccineA living, non-virulent form of a pathogenic micro-organism or virus used to elicit an antibody response for the protection against infection by a virulent…
living modified organism(Abbreviation: LMO). "Living organism that possess a novel combination of genetic material obtained through the use of modern biotechnology " (Convention…
LocalizeDetermination of the original position (locus) of a gene or other marker on a chromosome.
locus(LOH-kuss) Specific place where something is located or occurs. It may refer to a specific place on the body (such as an acupuncture point) or the place…
Locus (pl. loci)The position on a chromosome of a gene or other chromosome marker; also, the DNA at that position.
long interspersed nuclear element(Abbreviation: LINE). Families of common DNA elements, of average length 6.5 kb, which are dispersed at numerous locations within the genome.
long templateA DNA strand, synthesized during PCR, which has a primer sequence at one end but is extended beyond the site that is complementary to the second primer at…
long terminal repeat(Abbreviation: LTR). A characteristic sequence of nucleotides that occurs at each end of a retrovirus element that has become integrated into the host…
long-day plantPlants requiring a period of short nights before the switch from vegetative to reproductive growth can be initiated. See: Short-day plant.
Long-Range Restriction MappingRestriction enzymes are proteins that cut DNA at precise locations. Restriction maps depict the chromosomal positions of restriction-enzyme cutting sites.
Long-term self-renewalThe ability of stem cells to renew themselves by dividing into the same non-specialized cell type over long periods (many months to years) depending on…
loop bioreactorFermenters in which material is cycled between a bulk tank and a smaller tank or loop of pipes.
luteinizing hormoneA pituitary hormone which causes growth of the yellow body of the ovary and also stimulates activity of the interstitial cells of the testis.
luxury consumptionNutrient absorption by an organism in excess of that required for optimum growth and productivity.
lyaseAny of a class of enzymes that catalyse either the cleavage of a double bond and the addition of new groups to a substrate, or the formation of a double…
Lymph NodeA small rounded or bean-shaped mass of lymphatic tissue that helps the body's immune system.
Lymph nodes(LIMF nohdz): Small glands that help the body fight infection and disease. They filter a fluid called lymph and contain white blood cells.
Lymphatic system(lim-FA-tik SIS-tem) The tissues and organs that produce, store, and carry white blood cells that fight infections and other diseases.
Lymphocyte(LIM-foh-site) A type of white blood cell. Lymphocytes have a number of roles in the immune system, including the production of antibodies and other…
Lymphoid(LIM-foyd) Referring to lymphocytes, a type of white blood cell. Also refers to tissue in which lymphocytes develop.
lymphokineGeneric name for proteins that are released by lymphocyte s to act on other cells involved in the immune response.
lymphoma(lim-FOH-muh) Cancer that begins in cells of the immune system. There are two basic categories of lymphomas.
lysogenyA condition in which a bacteriophage genome (pro-phage ) survives within a host bacterium, either as part of the host chromosome or as part of an…
lysosomeA sac-like compartment inside a cell that has enzymes that can break down cellular components that need to be destroyed.
lysozymeA naturally occurring enzyme extracted from egg white protein and other animal and plant sources, which attacks the cell wall of gram-positive bacteria…
lyticHaving to do with lysis. In biology, lysis refers to the disintegration of a cell by disruption of its plasma membrane.
lytic cycleThe steps in viral production that lead to cell lysis.
M13A single-stranded DNA bacteriophage used as a vector for DNA sequencing.
M13 strandThe single-stranded DNA molecule that is present in the infective form of bacteriophage M13.
MAAPAbbreviation for multiple arbitrary amplicon profiling.
macerateTo disintegrate tissue to disrupt cells. Commonly achieved via mechanical shearing, plasmolysis or enzymatic cell wall degradation.
macromoleculeAny high molecular weight molecule. Often used as a synonym for polymers.
macronutrientA major chemical element essential for normal growth and development. In tissue culture media, macronutrients are those required in concentrations above 0.
macrophageA type of white blood cell that surrounds and kills microorganisms, removes dead cells, and stimulates the action of other immune system cells.
mad cow diseaseColloquial term for bovine spongiform encephalopathy. See proteinaceous infectious particle
MADS boxA highly conserved DNA sequence motif found in a large family of transcription factors, most of which play important roles in developmental processes.
MagentaUsed in four color printing. Reflects blue & red and absorbs green.
major histocompatibility antigenA cell-surface protein or glycoprotein that allows the immune system to distinguish foreign or "non-self" from "self". A better term is histoglobulin.
major histocompatibility complex(Abbreviation: MHC). The large cluster of genes that encode the major histocompatibility antigens in mammals.
Major histocompatibility complex (MHC)A group of genes that code for cell-surface histocompatibility antigens. These antigens are the primary reason why organ and tissue transplants from…
malformationA structural defect inherited in an organ or part of an organ that results from abnormal fetal development. See also syndrome
Malignant(muh-LIG-nunt) Cancerous. Malignant tumors can invade and destroy nearby tissue and spread to other parts of the body.
malt extractA mixture of organic compounds prepared from malt, used as a culture medium additive.
maltingEnzymatic reduction of starch to sugars in germinating grain, used in brewing.
mammary glandGlandular organ located on the chest. The mammary gland is made up of connective tissue, fat, and tissue that contains the glands that can make milk.
management of farm animal genetic resourcesThe sum total of technical, policy and logistical operations involved in understanding (characterization), using and developing (utilization), maintaining…
mannitol(MA-nih-TOL) A drug used to decrease swelling of the brain and to treat kidney failure.
mannoseA hexose component of many polysaccharides, occasionally used as a carbohydrate source in plant tissue culture media.
MAP1. verb: to determine the relative positions of loci (genes or DNA sequences) on a chromosome.
map distanceThe standard measure of genetic distance between loci, expressed in centiMorgans (cM) or map units .
map unitOne centiMorgan (1 cM) See: map distance; crossing-over unit.
mappingDetermining the physical location of a gene or genetic marker on a chromosome. (See Continuous map, Genetic map, Physical map.)
markerA diagnostic indication that disease may develop.
marker geneA gene of known function or known location, used for marker-assisted selection or genetic studies.
marker peptideA portion of fusion protein that facilitates its identification or purification.
marker-assisted introgressionThe use of DNA markers to increase the speed and efficiency of introgression of a new allele(s) or gene(s) into a breeding population.
marker-assisted selection(Abbreviation: MAS). The use of DNA markers to improve response to selection in a population.
mass selectionAs practised in plant and animal breeding, the selection ofa number of individuals, on the basis of their individual phenotypes, to interbreed to form the…
Mass spectrometrythis technique can be used to both measure and analyze molecules under study. It involves introducing enough energy into a target molecule to cause its…