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Home >> Dictionary of Bioinformatics, Biochemistry, Biotechnology >> Tay Sacha Disease, Telomeres
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Tautomerism Alternative structures that differ only in the location of hydrogen atoms. The amino and oxo groups of purines, pyrimidines and their derivatives exist in tautomeric equilibrium. The amino groups form an aminolimino pair while the oxo groups, a keto/enol pair of tautomers. The keto tautomer is called a lactam ring while the enol tautomer is the lactim ring.
Taxol A plant alkaloid that stabilises microtubules and blocks mitosis. It is used as a cancer chemotherapeutic agent
Taxonomy The science of classification.
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Tay-Sachs disease An inborn error of metabolism characterised by a deficiency of hexosaminidase Aassociated with accumulation of sphingolipid in the brain and spleen, neurodegeneration and death at an early age. Ashkenazi Jews are at high risk of developing Tay-Sachs than other ethnic groups. The clinical symptoms in the infantile form include delayed development, progressive neurological deterioration, seizures, cherry red spots and augmented startle response to sound. The clinical manifestations in juvenile-onset type include dementia, seizures and ocular findings. The adult form is slowly progressive with ataxia, lower motor neuron disease and recurrent psychoses
TBLASTN A bioinformatics tool that compares a protein query sequence a gainsta nucleotide sequence database dynamically translated in all reading frames.
TBLASTX A bioinformatics tool that compares the six-frame translations of a nucleotide query sequence against the six-frame translations of a nucleotide sequence database.
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TBP (TATA-binding protein) A monomeric eukaryotic protein that recognises and binds to the TATA box. The inner surface of TBP binds to the minor groove of DNA forming a 'saddle' structure, while the outer surface binds other proteins. Binding of TBP causes DNA bending that functions as a physical landmark for binding other general transcription factors.
TBP-associated factors See TAFs.
TCA cycle See tricarboxylic acid cycle.
TCD50 (Tissue culture dose 50%) That quantity of a viral suspension which when inoculated into tissue cultures causes degeneration of 50% of the culture.
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TCP/IP Transmission Control Protocol/ Internet Protocol. Protocols that regulate data packaging, reassembly (TCP) and how it is addressed and routed (IP) over the Internet.
Technology transfer The process of transferring discoveries made by basic research institutions, such as universities and government laboratories, to the commercial sector for development into useful products and services.
Teichoic acid A long polymer of glycerol ribitol joined together by phosphate groups. It is a structural component of the outer cell wall of Gram-positive bacteria
Telnet An Internet protocol that permits users to connect to computers at remote locations and use these computers as if they were physically sitting at that computer.
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Telocentric A monocentric chromosome with a terminal centromere.
Telogen An agent which causes premature termination of replication such as 2',3' -dideoxynucleotides.
Telomerase Ribonucleoprotein enzyme that replicates telomeric ends of chromo
somes. Telomerases have been isolated from microorganisms, plants, animals and humans. The enzyme is absent in many human somatic cells but found in germ-line cells. Telomere length aids in counting the number of cell divisions. Telomere shortening is believed to be responsible for ageing. Telomerase activity has been detected in normal cells with high proliferating activity as well as in malignant cells. The immortalisation of cancer cells may be due to high telomerase activity. The presence of telomerase in tumor cells and its absence in normal cells makes the enzyme a potential target for anticancer agents.
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Telomerase RNA A nuclear RNA containing the template for telomere repeats the forms part of telomerase.
Telomeres Extremely short, highly repetitive sequences of TG-rich nucleotides at the ends of linear chromosomes. They are conserved in protozoa, fungi, plants and mammals. The total length of these sequences varies considerably between species. While ciliates have as little as 36bp of telomeric DNA, mice contain up to 50 kb. In humans, the telomere sequence TTAGGG extends for 10,000 nucleotides. Since they are rich in G residues, the telomeres can form novel folded structures containing non-Watson-Crick base pairing such as the G quartet. These unusual structures may prevent enzymatic degradation of telomeres. Telomeres provide terminal stability to the chromosome and ensure its survival. They prevent shortening of the chromosome, which occurs due to the inability to replicate the ends of linear DNA molecules
Telomeric sequences Sequences at the ends of DNA strands essential for synthesising the ends of the lagging strand. These are present on the ends of the chromosomes and are useful in constructing yeast artificial chromosomes.
Telophase The final stage in each mitotic or meiotic division, in which the chromosomes are assembled at the poles of the division spindle.
TEM See transmission electron microscope.
Temperate phage A lysogenic phage (virus). A phage that invades but does not destroy (lyse) the bacterial (host) cell. However, it may subsequently enter the lytic cycle and destroy the bacterial host. See Lysogeny.
Temperature-sensitive mutation A mutation that generates a gene product which is functional at low temperature but inactive at higher temperature.
Temperature-sensitive protein A protein which is functional at a particular temperature losing its function at another (generally higher) temperature.
Template A pattern or mould. An RNA or single-stranded DNA molecule using which a complementary nucleotide strand is synthesised. DNA which stores genetic information functions as a model or template for the formation of complementary DNA strands or transcribed into mRNA.
Template strand The polynucleotide strand used as a mould by a polymerase for synthesising the new strand.
Tenoposide (VM-26) An anticancer agent derived from roots of Mayapple that acts by interrupting DNA topoisomerase II.
Tentative consensus (TC) The identification of a sequence from an EST cluster that represents part or all of a complete gene. TCs are generally determined by clustering ESTs to allow for sequencing errors, artefacts such as chimeric clones, and naturally occurring biological phenomena such as alternative splicing. Creation of a cluster permits generation of a consensus sequence and identification of a long ORF that would suggest the possibility of that consensus representing a bona fide gene.
Tentative human consensus sequences (THCs) A consensus sequence generated from human EST fragments that can be validated by comparison against databases of known human gene sequences, human genomic sequences, or by identification of the ORFs or other sequence features contained within the consensus as belonging to a known human gene product.
Ter sequence A specific sequence of 20 bp where termination of replication occurs in E.coli. The ter sequence contains two pairs of inverted repeats, which bind a protein factor called Tus (for terminus utilisation substance). The Tus-Ter complex arrests a replication fork in one direction. Consequently, the replication fork, which encounters the complex first, halts whereas the other fork halts when it encounters the arrested fork.
Tera becquerel (51 unit, TBq) 1012 Bq or 27.027 Ci
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