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.