0.5 Glossary  (Page 17/18)

T

• T-cell receptors (TCR) molecules on T cells involved in the recognition of processed foreign epitopes presented with MHC I or MHC II
• T lymphocyte lymphocyte that serves as the central orchestrator, bridging humoral, cellular, and innate immunity, and serves as the effector cells of cellular immunity; T cell
• taeniasis infection caused by Taenia or Diphyllobothrium
• tail fiber long protein component on the lower part of a phage used for specific attachment to bacterial cell
• tail pins points extended at the base of a bacteriophage sheath that, along with tail fibers, lead to phage attachment to a bacterial cell
• tapeworms segmented, hermaphroditic, parasitic flatworms (Platyhelminthes)
• tartar calcified heavy plaque on teeth, also called dental calculus taxonomy the classification, description, identification, and naming of living organisms
• T-dependent antigen a protein antigen that is only capable of activating a B cell with the cooperation of a helper T cell
• TDP thermal death point is the lowest temperature at which all microorganisms are killed in a 10-minute exposure
• TDT thermal death time is the length of time needed to kill all microorganisms in a sample at a given temperature
• telomerase enzyme that attaches to the end of a linear chromosome and adds nucleotides to the 3’ end of one of the DNA strands, maintaining the telomere sequence, thus preventing loss of DNA from the end of the chromosome
• telomere repetitive, noncoding sequence found at the end of a linear eukaryotic chromosome that protects the genes near the end of the chromosome from deletion as the DNA molecule is repeatedly replicated
• temperate phage bacteriophage that can incorporate viral genome into the host cell chromosome and replicate with the host cell until new viruses are produced; a phage that undergoes the lysogenic cycle
• teratogenic able to disrupt the normal development of a fetus in utero
• terbinafine antifungal drug of the allylamine class that is used topically for the treatment of dermatophytic skin infections
• termination of DNA replication stage of replication during which DNA replication is halted once the chromosome has been fully replicated
• termination of transcription stage of transcription that occurs when RNA polymerase has reached specific DNA sequences, leading to release of the enzyme from the DNA template, freeing the RNA transcript and, thus, halting transcription
• termination of translation stage of translation during which a nonsense codon aligns with the A site, signaling release factors to release of the polypeptide, leading to the dissociation of the small and large ribosomal subunits from the mRNA and from each other
• tertiary structure large-scale, three-dimensional structure of a polypeptide
• test sensitivity probability that a diagnostic test will find evidence of the targeted disease when the pathogen is present
• test specificity probability that a diagnostic test will not find evidence of the targeted disease when the pathogen is absent
• testes (singular testis ) pair of glands located in the scrotum of males that produce sperm and testosterone
• tetanus bacterial disease caused by exotoxin produced by Clostridium tetani that causes a rigid paralysis
• tetracyclines class of protein synthesis inhibitors that bind to the 30S subunit, blocking the association of tRNAs with the ribosome during translation
• T _H 1 cells subtype of T cells that stimulate cytotoxic T cells, macrophages, neutrophils, and NK cells
• T _H 17 cells subtype of T cell that are essential for defense against specific pathogens and infections, such as chronic mucocutaneous infections with C. albicans
• T _H 2 cells subtype of T cells that stimulate B cells and direct their differentiation; also involved in directing antibody class switching
• thallus body of fleshy fungi (more generally, a body without a root, stem, or leaf) that commonly co-occurs with HIV infection; the microbes move to the lymphatic system in the groin
• thermophile a microorganism that grows best at warm temperatures, typically between about 50 °C and 80 °C
• thin sections thin slices of tissue for examination under a TEM
• thioglycolate medium medium designed to test the aerotolerance of bacteria; it contains a low concentration of agar to allow motile bacteria to move throughout the medium
• thioglycolate tube culture contains reducing medium through which oxygen diffuses from the tube opening, producing a range of oxygen environments down the length of the tube
• thrombocytes see platelets
• thylakoids a highly dynamic collection of membranous sacs found in the stroma of chloroplasts; site of photosynthesis
• thymic selection a three-step process of negative and positive selection of T cells in the thymus
• thymine dimer covalent linkage between two adjacent thymine bases on exposure to ultraviolet radiation
• thymine pyrimidine nitrogenous base found only in DNA nucleotides
• tincture solution of an antiseptic compound dissolved in alcohol
• T-independent antigen a nonprotein antigen that can activate a B cell without cooperation from a helper T cell
• tinea any cutaneous fungal infection caused by dermatophytes, such as tinea corporis, tinea capitis, tinea cruris, and tinea pedis
• tinea capitis cutaneous mycosis of the scalp; also known as ringworm of the scalp
• tinea corporis cutaneous mycosis of the body; also known as ringworm of the body
• tinea cruris cutaneous mycosis of the groin region; also known as jock itch
• tinea pedis cutaneous mycosis of the feet; also known as athlete’s foot
• tissue tropism tendency of most viruses to infect only certain tissue types within a host
• titer concentration obtained by titration; the reciprocal of a measurement of biological activity determined by finding the dilution of an unknown (e.g., antigen-specific antibody in an antiserum) that shows the defined end-point; always expressed as a whole number
• tolerance lack of an anti-self immune response
• toll-like receptors (TLRs) pathogen recognition receptors (PRRs) that may be found on the external surface of phagocytes or facing inward in interior compartments
• tonsillitis inflammation of the tonsils
• topoisomerase type of enzyme that helps maintain the structure of supercoiled chromosomes, preventing overwinding of DNA during certain cellular processes like DNA replication
• topoisomerase II enzyme responsible for facilitating topological transitions of DNA, relaxing it from its supercoiled state
• total magnification in a light microscope is a value calculated by multiplying the magnification of the ocular by the magnification of the objective lenses
• toxemia presence of toxins in the blood
• toxic shock syndrome severe condition marked by the loss of blood pressure and blood clot formation caused by a bacterial superantigen, toxic shock syndrome toxin
• toxigenicity ability of a pathogen to produce toxins to cause damage to host cells
• toxin poison produced by a pathogen
• toxoid vaccine vaccine that contains inactivated bacterial toxins
• toxoplasmosis typically asymptomatic protozoan infection caused by Toxoplasma spp. and transmitted through contact with cysts in cat feces; infections in pregnant women may cause birth defects or miscarriage
• trace element indispensable element present in cells in lower amounts than macronutrients; also called micronutrient
• trachea also known as the windpipe, this is a stiffened tube of cartilage that runs from the larynx to the bronchi
• trachoma a type of conjunctivitis, caused by Chlamydia trachomatis , that is a major cause of preventable blindness
• transcription bubble region of unwinding of the DNA double helix during transcription
• transcription factors proteins encoded by regulatory genes that function by influencing the binding of RNA polymerase to the promoter and allowing its progression to transcribe structural genes
• transcription process of synthesizing RNA using the information encoded in DNA
• transcriptomics the study of the entire collection of mRNA molecules produced by cells; involves monitoring differences in gene expression patterns between cells at the mRNA level
• transduction mechanism of horizontal gene transfer in bacteria in which genes are transferred through viral infection
• transendothelial migration process by which circulating leukocytes exit the bloodstream via the microvascular endothelium
• transfection the introduction of recombinant DNA molecules into eukaryotic hosts
• transformation mechanism of horizontal gene transfer in bacteria in which naked environmental DNA is taken up by a bacterial cell
• transgenic describing an organism into which foreign DNA from a different species has been introduced
• transient microbiota microorganisms, sometimes pathogenic, that are only temporarily found in the human body
• transition reaction reaction linking glycolysis to the Krebs cycle, during which each pyruvate is decarboxylated and oxidized (forming NADH), and the resulting two-carbon acetyl group is attached to a large carrier molecule called coenzyme A, resulting in the formation of acetyl-CoA and CO; also called the bridge reaction
• translation (protein synthesis) process of protein synthesis whereby a ribosome decodes an mRNA message into a polypeptide product
• transmissible spongiform encephalopathy degenerative disease caused by prions; leads to the death of neurons in the brain
• transmission electron microscope (TEM) a type of electron microscope that uses an electron beam, focused with magnets, that passes through a thin specimen
• transmittance the amount of light that passes through a medium
• transparency the property of allowing light to pass through
• transport vesicle membranous sac that carries molecules between various components of the endomembrane system
• transposition process whereby a DNA sequence known as a transposon independently excises from one location in a DNA molecule and integrates elsewhere
• transposon (transposable element) molecule of DNA that can independently excise from one location in a DNA molecule and integrate into the DNA elsewhere
• trench fever louseborne disease caused by Bartonella quintana and characterized by high fever, body aches, conjunctivitis, ocular pain, severe headaches, and severe bone pain
• trench mouth a severe form of gingivitis, also called acute necrotizing ulcerative gingivitis
• treponemal serologic tests tests for syphilis that measure the amount of antibody directed against antigens associated with Treponema pallidum
• triacylglycerol three fatty acids chemically linked to a glycerol molecule; also called a triglyceride
• triazoles ergosterol biosynthesis inhibitors used to treat several types of systemic yeast infections; exhibit more selective toxicity than the imidazoles and are associated with fewer side effects
• tricarboxylic acid cycle see Krebs cycle
• trichinosis soil-transmitted intestinal infection caused by the nematode Trichinella spiralis ; associated with cyst formation
• trichomoniasis a common STI caused by Trichomonas vaginalis
• trichuriasis intestinal infection caused by the whipworm Trichuris trichiura
• triglyceride three fatty acids chemically linked to a glycerol molecule; also called a triacylglycerol
• trimethoprim synthetic antimicrobial compound that functions as an antimetabolite to an enzyme in the bacterial folic acid synthesis pathway
• tRNA small type of stable RNA that carries the correct amino acid to the site of protein synthesis in the ribosome and base pairs with the mRNA to allow the amino acid it carries to be inserted in the polypeptide chain being synthesized
• trophozoite a life cycle phase in which protists are actively feeding and growing
• tubercle small, rounded lesion
• tuberculosis life-threatening form of microbial infection marked by the presence of acid-fast bacteria growing in nodules (especially in the lungs)
• tularemia infection of the lymphatic system by Francisella tularensis ; also known as rabbit fever
• tumbles (tumbling) random, circuitous movement of a bacterial cell, propelled by clockwise flagellar rotation
• tumor collection or aggregate of cells; can be benign (noncancerous) or malignant (cancerous)
• tumor-inducing (T _i ) plasmid a naturally occurring plasmid of the bacterium Agrobacterium tumefaciens that researchers use as a shuttle vector to introduce a desired DNA fragment into plant cells
• turbidity cloudiness of a culture due to refraction of light by cells and particles
• two-photon microscope a microscope that uses long-wavelength or infrared light to fluoresce fluorochromes in the specimen
• tympanic membrane also referred to as the ear drum, this structure separates the outer and middle ear
• type 1 diabetes mellitus hyperglycemia caused by an autoimmune disease affecting insulin production by β cells of the pancreas
• type I hypersensitivity rapid-onset allergic reaction due to cross-linking of antigen-specific IgE on the outside of mast cells, resulting in release of inflammatory mediators
• type II hypersensitivity cytotoxic reaction triggered by IgG and IgM antibodies binding to antigens on cell surfaces
• type III hypersensitivity inflammatory reaction induced by formation of immune complexes and their deposition in tissues and blood vessels
• type IV hypersensitivity delayed T-cell-mediated inflammatory reaction that takes longer to manifest than the first three hypersensitivity types, due to the need for activation of antigen-presenting cell and T-cell subsets
• typhoid fever serious illness caused by infection with certain serotypes of Salmonella