Biotechnology and Genetics terms starting with N

118 terms

naked bud A bud not protected by bud scales.
narrow-host-range plasmid A plasmid that can replicate in one, or at most a few, different bacterial species.
narrow-sense heritability The proportion of the phenotypic variance that is due to variation in breeding values; the proportion of the phenotypic variance that is due to additive…
National Institutes of Health (NIH) A nonregulatory agency which has oversight of research activities that the agency funds.
National Science Foundation (NSF) A nonregulatory agency which has oversight of biotechnology research activities that the agency funds.
native protein The naturally occurring form of a protein.
Natural killer cell A type of white blood cell that contains granules with enzymes that can kill tumor cells or microbial cells.
Natural selection The differential survival and reproduc- tion of organisms with genetic characteristics that enable them to better utilize environmental resources.
necrosis (ne-KRO-sis) Refers to the death of living tissues.
negative autogenous regulation Inhibition of the expression of a gene or set of co-ordinately regulated genes by the product of the gene or the product of one of the genes.
negative control system A mechanism by which a regulatory protein is required to turn off gene expression.
negative selection Selection against individuals possessing a certain character. Opposite: positive selection.
negative self-regulation See: negative autogenous regulation.
nematode Slender, unsegmented worms, often parasitic. Also known as eelworm, especially when phytoparasitic.
neo-formation See: organogenesis.
neomycin phosphotransferase II (Abbreviation: npt-II). An enzyme which detoxifies the antibiotic neomycin, used as a marker gene to select for successfully transformed cells in plant…
neoplasm (NEE-oh-PLA-zum) An abnormal mass of tissue that results when cells divide more than they should or do not die when they should.
neor Neomycin-resistance gene. See: antibiotic resistance marker gene, neomycin phosphotransferase II, selectable marker.
neoteny The retention of juvenile body characters in the adult state, or the occurrence of adult characters in the juvenile state.
Nestin An intermediate filament protein found in cells such as neural and pancreatic precursors.
net photosynthesis Photosynthetic activity minus respiratory activity, measured by the net absorption of carbon dioxide.
Neural crest A band of cells that extend lengthwise along the neural tube of an embryo and give rise to cells that form the cranial, spinal, and autonomic ganglia, as…
Neural plate A thickened band of ectoderm along the dorsal surface of an embryo. The nervous system develops from this tissue.
Neural stem cell A type of stem cell that resides in the brain, which can make new nerve cells (called neurons) and other cells that support nerve cells (called glia).
Neural stem cell (NSC) A stem cell found in adult neural tissue that can give rise to neurons, astrocytes, and oligodendrocytes.
Neural tube The embryological forerunner of the central nervous system.
Neuroectoderm The central region of the early embryonic ectoderm, which later forms the brain and spinal cord, as well as evolving into nerve cells of the peripheral…
Neuroepithelium A specialized epithelial structure that forms the termination of a nerve of a special sense, i.e.
neurofibromatosis An inherited progressive disorder in which tumors form on peripheral nerves. The tumors can be severely disfiguring and can also result in loss of hearing…
Neurofilament (NF) A type of intermediate filament found in nerve cells.
Neuron (NOOR-on) A type of cell that receives and sends messages from the body to the brain and back to the body.
Neuronal/neural stem cells cells capable of becoming tissues of the brain and central nervous system.
Neurons Nerve cells, the structural and functional unit of the nervous system. A neuron consists of a cell body and its processes-an axon and one or more…
Neurosphere A primitive neural tissue that arises when embryonic stem cells are grown in certain culture conditions.
neutral mutation A mutation that changes the nucleotide sequence of a gene, but has no observable effect on the fitness of the organism.
neutral theory The theory that much of evolution has been primarily due to random drift of neutral mutations.
neutropenia (noo-troh-PEE-nee-uh) An abnormal decrease in the number of neutrophils, a type of white blood cell.
neutrophil (NOO-tro-fil) A type of white blood cell.
NFT Abbreviation for nutrient film technique.
nick To break (or a break in) a phosphodiester bond in one of the strands of a double-stranded DNA molecule.
Nick translation A procedure for making a DNA probe in which a DNA fragment is treated with DNase to produce single-stranded nicks, followed by incorporation of…
nicked circle During the extraction of plasmid DNA from a bacterial cell, one strand of the DNA often becomes nicked.
Nicked circle (relaxed circle) During extraction of plasmid DNA from the bacterial cell, one strand of the DNA becomes nicked.
Niemann-Pick disease, type C (NPC) A disease that causes progressive deterioration of the nervous system by blocking movement of cholesterol within cells.
nif gene cluster Group of bacterial genes responsible for the biological fixation of atmospheric nitrogen.
NIH A federal agency in the U.S. that conducts biomedical research in its own laboratories; supports the research of non-Federal scientists in universities…
nitrate The form of nitrogen that can be used directly by plants; a major component of inorganic fertilizers.
nitrification The natural process in which nitrogen in plant and animal wastes is oxidized, first to nitrites and then to nitrates, through the action of soil-borne…
Nitrocellulose A membrane used to immobilize DNA, RNA, or protein, which can then be probed with a labeled sequence or antibody.
nitrogen assimilation The incorporation of nitrogen into the cells of living organisms.
Nitrogen fixation The conversion of atmospheric nitrogen to biologically usable nitrates.
Nitrogenous base The purines (adenine and guanine) and pyrimidines (cytosine, and thymine or uracil ) that are present in DNA and RNA.
Nitrogenous bases The purines (adenine and guanine) and pyrimidines (thymine, cytosine, and uracil) that comprise DNA and RNA molecules.
NMDA receptor (N-methyl-d-aspartate receptor). A neurotransmitter receptor for excitatory synapses.
NO Abbreviation for nucleolar organizer.
nod box A DNA sequence that controls the transcriptional regulation of Rhizobium nodulation genes.
Nodal A knob-like protrusion.
nodal culture The culture of a lateral bud and a section of adjacent stem tissue.
node Any device connected to network. PCs, servers, and printers are all nodes on the network.
nodular Term commonly used to describe the pebbly (rough) texture of a callus.
nodulation The formation of nodules on the roots of legumes following colonization by symbiotic nitrogen-fixing bacteria.
nodule (NOD-yool) A growth or lump that may be cancerous or noncancerous.
non repetitive DNA/RNA A nucleotide sequence which does not include a significant proportion of repetitive sequences of nucleotide s.
non-additive genetic variation The proportion of the total genetic variation in a population that does not respond to simple mass selection and that causes specific pairwise crosses to…
non-autonomous A term referring to biological units that cannot function by themselves; such units require the assistance of another unit, or "helper".
non-coding DNA The strand of DNA that does not carry the information necessary to make a protein.
non-coding strand See: antisense DNA.
non-directiveness The process by which genetic counselors advise clients toward a certain test or outcome, particularly related to child-bearing issues, without pressure or…
non-disjunction Failure of separation of homologous chromosomes or chromatids in mitosis or meiosis, resulting in too many chromosomes in some daughter cells and too few…
non-histone chromosomal protein In chromosomes, all of the proteins except the histones.
Non-Myeloablative ("Mini") Stem Cell Transplant A method used to prime a patient for a stem cell transplant by employing lower doses of chemotherapy and/or radiotherapy to damage the leukemia-producing…
non-target organism An organism which is affected by a treatment (e.g. pesticide application) for which it was not the intended recipient.
non-template strand The non-transcribed strand of DNA. Synonyms: sense strand, coding strand
non-virulent agent See: attenuated vaccine.
nonsense mutation A mutation which converts an amino-acid-specifying codon into a stop codon, e.g.
Nontarget organism An organism which is affected by an interaction for which it was not the intended recipient.
NOR Abbreviation for nucleolar organizer region.
Northern blot A technique analogous to Southern blotting, but involving the transfer of RNA from an to a membrane, prior to probing.
Northern blotting See Northern hybridization.
Northern hybridization (Northern blotting). A procedure in which RNA fragments are transferred from an agarose gel to a nitrocellulose filter, where the RNA is then hybridized…
Notochord Forms the axial skeleton in embryos of all chordates. In vertebrates, it is replaced partially or completely by vertebrae.
npt-II Abbreviation for neomycin phosphotransferase II.
NSF Lotus Notes Format Database File (i.e. database.nsf) Can be either an email database or the traditional type of fielded database.
nucellar embryo An embryo which has developed vegetatively from somatic tissue surrounding the embryo sac, rather than by fertilization of the egg cell.
nucellus Tissue forming the major part of the young ovule in which the embryo sac develops; Also known as megasporangium.
Nuclear reprogramming Restoration of the correct embryonic pattern of gene expression in a nucleus derived from a somatic cell and introduced into an oocyte.
Nuclear transfer A technology by which novel animals are generated by cloning a single diploid somatic cell.
Nuclear transfer (NT) The generation of a new animal nearly identical to another one by injection of the nucleus from a cell of the donor animal into an enucleated oocyte of…
Nuclease A class of enzymes that degrades DNA and/or RNA molecules by cleaving the phosphodiester bonds that link adjacent nucleotides.
Nucleic acid A macromolecule consisting of polymerized nucleotides . Two forms are found, DNA and RNA.
nucleic acid probe See: DNA probe.
Nucleic acids The two nucleic acids, deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), are made up of long chains of molecules called nucleotides.
Nuclein The term used by Friedrich Miescher to describe the nuclear material he discovered in 1869, which today is known as DNA.
nucleo-cytoplasmic ratio In a cell, the ratio of nuclear to cytoplasmic volume. This ratio is high in meristematic cells and low in differentiated cells.
nucleolar organizer (Abbreviation: NO). See: nucleolar organizer region.
nucleolar organizer region (Abbreviation: NOR). A chromosomal segment containing a large array of genes that encode ribosomal RNA; located at the secondary constriction of specific…
Nucleolar organizing region A part of the chromosome containing rRNA genes.
nucleolus An RNA -rich nuclear organelle in the nucleus of eukaryotic cells, produced by a nucleolar organizer.
nucleoplasm The non-staining or slightly chromophilic, liquid or semi-liquid, ground substance of the interphase nucleus and which fills the nuclear space around the…
nucleoprotein Conjugated protein composed of nucleic acid and protein; the material of which the chromosomes are made.