biology-dictionary_11-06-2009

Mosaic development A pattern of development, such as that of a mollusk, in which the early blastomeres each give rise to a speci ...

Multicellular Consisting of many cells Multigene family A collection of genes with similar or identical sequences, presumably of ...

N NAD + (nicotinamide adenine dinucleotide) Abbreviation of nicotinamide adenine dinucleotide, a coenzyme present in all cells t ...

Nephrons The tubular excretory unit of the vertebrate kidney. Neritic zone The shallow regions of the ocean overlying the contin ...

Neural crest A band of cells along the border where the neural tube pinches off from the ectoderm; the cells migrate to various ...

Neutral variation Genetic diversity that confers no apparent selective advantage. Neutron An electrically neutral particle (a pa ...

Node A point along the stem of a plant at which leaves are attached. Nodes of Ranvier The small gaps in the myelin sheath betwee ...

Noradrenaline A hormone, produced by the medulla of the adrenal gland, that increases the concentration of glucose in the blood, ...

Nuclear pores The nuclear envelope is composed of two membranes joined at regular intervals to form circular openings called nuc ...

Nucleotide The building block of a nucleic acid, consisting of a five-carbon sugar covently bonded to a nitrogenous base and a p ...

Oils Flammable substance, usually insoluble in water, and composed chiefly of carbon and hydrogen. Oils may be solids (fats and ...

Operator A segment of DNA that interacts with a repressor protein to regulate the transcription of the structural genes of an op ...

Organelle One of several formed bodies with a specialized function, suspended in the cytoplasm and found in eukaryotic cells. Or ...

Osmolarity Solute concentration expressed as molarity. Osmoregulation Adaptations to control the water balance in organisms livi ...

Ovaries The usually paired female or hermaphroditic reproductive organ that produces ova and, in vertebrates, estrogen and proge ...

Oxidative phosphorylation The production of ATP using energy derived from the redox reactions of an electron transport chain. Ox ...

Polysaccharides A carbohydrate which consists of a number of linked sugar molecules, such as starch or cellulose. Palisade cells ...

Parasite An organism that absorbs nutrients from the body fluids of living hosts. Parasitic Relating to or caused by parasites; ...

Passive transport The diffusion of a substance across a biological membrane. Pathogen An organism or a virus that causes disease ...

Pentose Any of a class of simple sugars having five carbon atoms per molecule. Ribose and deoxyribose are pentoses. Penetrance I ...