T tandem repeat sequences Multiple copies of the same base sequence on a
chromosome; used as a marker in physical mapping tar Short for Tape Archive. A UNIX command for copying files
to or restoring files from a backup tape. TATA box The name given to the commonly occurring substring "TATA"
that appears in the promotor region of many genes. tautomeric shift The spontaneous change of a molecule from one structural
isomer to another tautomers Structural isomers that are in dynamic equilibrium taxon A taxonomic group of any rank (e.g., species, genus,
kingdom) to which individual organisms are assigned taxonomy The principles and procedures according to which species
are named and assigned to taxonomic groups TCP/IP Transmission Control Protocol / Internet Protocol - An
internet protocol for communication between subnets. It is
designed to function well even in an unreliable subnet. tcsh The T shell. A UNIX command shell similar to csh, but
with more features. telnet An Internet protocol for remote login to a host
computer. telomere The ends of chromosomes. These specialized structures are
involved in the replication and stability of linear DNA
molecules. telomerase The enzyme that maintains the ends of eukaryotic
chromosomes by synthesizing telomeric repeat sequences. temperature sensitive mutation A type of conditional-lethal mutation; one that is
expressed only above a threshold temperature template The polynucleotide that is copied during strand synthesis
reaction catalyzed by a DNA or RNA polymerase template-dependent DNA synthesis Synthesis fo a DNA molecule on a DNA or RNA template template dependent RNA synthesis Synthesis of a RNA molecule on a DNA or RNA template template independent RNA polymerase An enzyme that polymerizes RNA without the use of a
template. For example during the addition of a Poly-A tail
to mRNA template strand The polynucleotide that acts as the template for RNA
synthnesis during the transcription of a gene. terminal deoxynucleotidyl transferase An enzyme that adds one or more nucleotides to the
3'-ends of DNA molecules terminal node The graphical representation of an extant taxon in a
phylogenetic tree termination codon A codon for which no normal tRNA exists, the presence of
which terminates the process of translation. The three
termination codons in the genetic code are UAG, UAA and
UGA. termination factor A protein that plays an ancillary role in termination of
transcription. terminator sequence One of several sequences on a bacterial genome involved
in termination of DNA replication tertiary structure In proteins and nucleic acids, the three-dimensional
structure of the molecule brought about by its folding upon
itself. test cross A genetic cross between a heterozygote and the recessive
homozygote. thermal cycle sequencing A DNA sequencing method that uses PCR to generate
chain-terminated polynucleotides. thermal stability The degree of resistance against denaturation or melting
by changes in temperature. One of the pyrimidine bases found in DNA. Tm The median melting temperature of duplex DNA Tn3 type transposon A type of DNA transposon that does not have flanking
insertion sequences topoisomerase topology the branching pattern of a phylogenetic tree totipotent Refers to a cell that is not committed to a single
developmental pathway and can hence give rise to all types
of differentiated cell. traceback The second stage of a dynamic programming alignment, in
which the alignment is found by following the pointers back
from the highest scoring position in the score matrix. trailer segment The untranslated region of a mRNA downstream of the
termination codon. trans The arrangement of two sequences or genes on different
chromosomes transcript A RNA copy of a gene. transcription The synthesis of a RNA molecule on a DNA template.The
process by which an RNA molecule is synthesized
complementary to the DNA in a gene. In eukaryotes, both the
introns and the exons are transcribed in the tRNA. The
introns are later spliced out, creating a mRNA transcription bubble The nonbase-paired region of the double helix, maintained
by RNA polymerase, within which transcription occurs transcription coupled repair A nucleotide excision repair process that results in
repair of the template strands of genes. transcription factor General term for a protein that aids in initiating or
regulating transcription. transcription factory The large structure attached to the nuclear matrix, the
site of RNA synthesis. transcription initiation The assembly upstream of a gene of the complex of
proteins that will subsequently copy the gene into RNA transcription-termination site The point at which the transcription of RNA is
terminated. In RNAs that are polyadenylated, it may or may
not be identical with the polyadenylation site. transcriptome The entire mRNA content of a cell transduction The transfer of host genetic information from one cell to
another by means of a virus. transduction mapping The use of transductin to map the relative positions of
genes in a bacterial genome transfer-messenger RNA A bacterial RNA involved in protein degradation transfer RNA (tRNA) The RNA molecule that transports a specific amino acid to
a growing amino acid chain, as directed by a specific codon
in the mRNA. transformant A cell that has become transformed by the uptake of naked
DNA transformation A process by which the genetic material carried by an
individual cell is altered by incorporation of exogenous DNA
into its genome. transformation mapping The use of transformation to map the relative positions
of genes in a bacterial chromosome. transgenic organism An organism into which the genes of other species have
been engineered transition The a change in the DNA by mutation or engineering that
causes a substitution of a purine for a purine (C to a T) or
a pyrimidine to a pyrimidine (A to a G or vice versa). translation The derivation of the amino acid sequence of a
polypeptide from the sequence of a mRNA molecule via tRNA
intermediates which occurs in association with a
ribosome. translocation The movement of a ribosome along a mRNA molecule during
translation transposable element A sequence that can move about in the genome of an
organism transposase An enzyme that catalyzes transposition of a transposable
genetic element transposition The movement of genetic material from on egenomic
location to another transposon A transposable element carrying additional genes beside
those encoding the transposition functions transversion The a change in the DNA by mutation or engineering that
causes a substitution of a purine for a pyrimidine or vice
versa. trinucleotide repeat expansion disease A disease that results from the expansion fo an array of
trinucleotide repeats in or near to a gene. For example
Huntington's disease. triplet binding assay A technique for determining the coding specificity of a
triplet of nucleotides triplex A DNA structure comprising three polynucleotides.
Important in antisense oligonucleotide DNA therapy. trisomy The presence of three copies of a chromosome in an
otherwise diploid cell twintron A composite structure made up of two or more Group II
and/or Group III introns embedded in each other. twofold degenerate site A nucleotide site in the coding region at which one of
the three possible nucleotide changes is synonymous and the
other two are nonsynonymous.
