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talonid: A distal shelf
on a tooth.
talus (astragalus):
Anklebone.
taphonomy: Study of
the processes that effect the remains of organisms from the death
of an organism through its fossilization.
tarsals: Small bones
of the ankle and foor. In humans these are the talus, calcaneus,
navicular, cuboid, and three cuneiforms.
TATA element: See Goldberg-Hogness
box.
taurodont: Teeth having
enlarged pulp cavities in their roots.
tautomeric shift: The
change in the chemical form of a DNA (or RNA) base.
tautomers: Alternate
chemical forms in which DNA (or RNA) bases are able to exist.
taxon: A monophyletic
group of organisms recognized as a formal unit, at any level of
a hierarchic classification.
taxonomy: The theory
and practice of classifying organisms.
technology: The techniques
used to produce artifacts.
tectonic movements:
Displacements in the plates that make up the earth's crust, often
responsible for the occurrence of raised beaches.
tektites: Streamlined
glassy objects found in some soils that result from meteoric impacts
that throw silicon-rich material into the upper atmosphere that
fuses into a glass as it heats up during its return.
tell: A Near Eastern
term that refers to a mound site formed through successive human
occupation over a very long time span.
telocentric chromosome:
A chromosome that has the centromere more or less at one end.
telomere-associated
sequences: Repeated, complex DNA sequences extending from the molecular
gene of chromosomal DNA, suspected to mediate many of the telomere-specific
interactions.
telophase: A stage
during which the migration of the daughter chromosomes to the two
poles is completed.
telophase II: The last
stage of meiosis II during which a nuclear membrane forms around
each set of chromosomes, and cytokinesis takes place.
template strand: The
unwound single strand of DNA on which new strands are made (following
complementary base pairing rules).
temporal bone: Complex
bone on the side and base of the cranium that includes the ear,
mandibular joint, and a portion of the side of the braincase.
temporal fossa: The
space enclosed by the side of the skull and the zygomatic arch,
which is occupied by the temporalis muscle as it passes from its
mandibular attachment to its attachment on the cranium.
temporal line: The
line caused by the edge of the temporalis muscle where it attaches
along the cranial vault. There are two lines, an inferior line from
the deep part of the muscle and a superior line from the superficial
part.
temporalis muscle:
A fan-shaped muscle that moves the jaw in mastication and creates
force between the teeth, joining the inside of the mandibular ramus
and the side and rear of the skull.
temporonuchal crest:
A compound crest on the back of the skull formed by convergence
of the temporal line of the nuchal crest.
tendon: A strong, inelastic
cord of connective tissue joining muscle to bone.
tephra: Volcanic ash.
In the Mediterranean, for example, deep-sea coring produced evidence
for the ash fall from the eruption of Thera, and its stratigraphic
location provided important information in the construction of a
relative chronology.
termination factors
(release factors; RF): The specific proteins in polypeptide synthesis
(translation) that read the chain termination codons and then initiate
a series of specific events to terminate polypeptide synthesis.
terminations: In glacial
studies, the midpoints in deglaciations leading to interglacial
periods.
terminator: See transcription
terminator sequence.
terrestrial: On the
ground.
terrestrial quadruped:
Ground-living animal that moves about primarily on all four limbs.
territory: Part of
a home range that is exclusive to a group of animals and is actively
defended from other groups of the same species.
testcross: A cross
of an individual of unknown genotype, usually expressing the dominant
phenotype, with a homozygous recessive individual in order to determine
the genotype of the individual.
testis-determining
factor: Gene product in placental mammals that sets the switch toward
male sexual differentiation.
tetrad analysis: Genetic
analysis of all the products of a single meiotic event. Tetrad analysis
is possible in those organisms in which the four products of a single
nucleus that has undergone meiosis are grouped together in a single
structure.
tetrasomy: The aberrant,
aneuploid state in a normally diploid cell or organism in which
an extra chromosome pair results in the presence of four copies
of one chromosome type and two copies of every other chromosome
type.
tetratype (T): One
of the three types of tetrads possible when two genes are segregating
in a cross. The T tetrad contains two parental and two recombinant
nuclei, one of each parental type and one of each recombinant type.
thermoluminescence
(TL): A dating technique that relies indirectly on radioactive decay,
overlapping with radiocarbon in the time period for which it is
useful, but also has the potential for dating earlier periods. It
has much in common with electron spin resonance (ESR).
Thiessen polygons:
A formal method of describing settlement patterns based on the territoral
divisions centered on a single site; the polygons are created by
drawing straight lines between pairs of neighboring sites, then
at the mid-point along each of these lines, a second series of lines
are drawn at right angles to the first. Linking the second series
of lines creates the Thiessen polygons.
thin-section analysis:
A technique whereby microscopic thin sections are cut from a stone
object or potsherd and examined with a petrological microscope to
determine the source of the material.
thoracic: Pertaining
to the thorax (chest), especially the ribbearing vertebrae below
the cervical and above the lumbar vertebrae.
Three Age System: A
classification system devised by C.J. Thomsen for the sequence of
technological periods (stone, bronze, and iron) in Old World prehistory.
It established the principle that by classifying artifacts, one
could produce a chronological ordering.
three-point testcross:
A test involving three genes within a relatively short section of
the chromosome. It is used to map genes for their order in the chromosome
and for the distance between them.
thymine (T): A pyrimidine
base found in DNA but not in RNA. In double-stranded DNA, thymine
pairs with adenine.
tibia: Long bones of
the lower leg, between the knee and the foot.
tomography: A CAT scan
is a radiographic technique that can display "slices"
taken through bones or skulls that will show the shape and extent
of internal cavities.
tool: An artifact with
a functional use. Curated tools are kept for use in the future,
while expedient tools are made in response to an immediate need.
toothpick grooves:
Elongate grooves between adjacent teeth, usually on the roots just
below the crown level and marked on their facing sides.
topoisomerases: A class
of enzymes that catalyze the supercoiling of DNA.
torsion: Twisting.
torus: A smooth rounded
ridge or protuberance.
totemism: Symbolic
association between a social group (e.g., a lineage or clan) and
a kind of bird, plant, or natural phenomenon. In "classic"
forms, a member of the social group has some special religious relationship
(e.g., a food taboo) toward members of the natural species.
totipotency: The capacity
of a nucleus to direct events through all the stages in development
and therefore produce a normal adult.
trabecular bone: See
cancellous bone.
trace element analysis:
The use of chemical techniques, such as neutron activation analysis,
or X-ray fluorescence spectrometry, for determining the incidence
of trace elements in rocks. These methods are widely used in the
identification of raw material sources for the production of stone
tools.
trailer sequenc: The
sequence of the mRNA molecule beginning at the end of the amino
acid-coding sequence and ending at the 3' end of the mRNA. The trailer
sequence is not translated and varies in length from molecule to
molecule.
trajectory: In systems
thinking, this refers to the series of successive states though
which the system proceeds oevr time. It may be said to represent
the long-term behavior of the system.
transconjugants: In
bacteria, the recipients inheriting donor DNA in the process of
conjugation.
transcription: The
transfer of information from a double-stranded DNA molecule to a
single-stranded RNA molecule. It is also called RNA synthesis.
transcriptional control:
The first level of control of gene expression in eukaryotes. This
level involves regulating whether or not a gene is to be transcribed
and the rate at which transcripts are produced.
transcription factors
(TFs): Specific proteins that are required for the initiation of
transcription by each of the three eukaryotic RNA polymerases. Each
polymerase uses its own set of TFs.
transcription terminator
sequence (terminator): A transcription regulatory sequence located
at the distal end of a gene that signals the termination of transcription.
transdetermination:
During development, a process whereby an imaginal disc does not
totally dedifferentiate but switches to another determined path.
trans-dominant: The
phenomenon of a gene or DNA sequence controlling genes that are
on a different piece (strand) of DNA.
transducing phage:
The phage that is the vehicle by which genetic material is shuttled
between bacteria.
transducing retroviruses:
Retroviruses that have picked up an oncogene from the cellular genome.
transductants: In bacteria,
the recipients inheriting donor DNA in the process of transduction.
transduction: A process
by which bacteriophages mediate the transfer of bacterial genetic
information from one bacterium (the donor) to another (the recipient);
a process whereby pieces of bacterial DNA are carried between bacterial
strains by a phage.
transfer RNA (tRNA):
One of the hour classes of RNA molecules produced by transcription
and involved in protein synthesis; molecules that bring amino acids
to the ribosome, where they are matched to the transcribed message
on the mRNA.
transformant: The genetic
recombinant generated by the transformation process.
transformation: 1)
A process in which genetic information is transferred by means of
extracellular pieces of DNA in bacteria 2) The failure of cells
to remain constrained in their growth properties and give rise to
tumors.
transgene: A gene introduced
into the genome of an organism by genetic manipulation in order
to alter its genotype.
transgenic organism:
An organism that has had its genotype altered by the introduction
of a new gene into its genome by genetic manipulation.
transitional mutation:
A specific type of base-pair substitution mutation that involves
a change in the DNA from one purine-pyrimidine base pair to the
other purine-pyrimidine base pair at a particular site (e.g., AT
to GC).
transit peptidase:
The enzyme that removes transit sequences from proteins transported
into organelles.
transit sequences:
The extra sequences at the N-terminal ends of proteins that are
necessary and sufficient for posttranslational transport into organelles.
translation (protein
synthesis): The conversion in the cell of the mRNA base sequence
information into an amino acid sequence of a polypeptide.
translational control:
The regulation of protein synthesis by ribosome synthesis among
mRNAs.
translocation (transposition):
1) A chromosomal mutation involving a change in position of a chromosome
segment (or segments) and the gene sequences it contains 2) In polypeptide
synthesis, translocation is the movement of the ribosome, one codon
at a time, along the mRNA toward the 3' end.
transmission genetics
(classical genetics): A subdivision of the science of genetics primarily
dealing with how genes are passed from one individual to another.
transport control:
Regulating the number of transcripts that exit the nucleus to the
cytoplasm.
transposable element:
A genetic element of chromosomes of both prokaryotes and eukaryotes
that has the capacity to mobilize itself and move from one location
to another in the genome.
transposase: A enzyme
encoded by the IS element of a transposon that calalyzes transposition
activity of a transposable element.
transposon (Tn): A
mobile DNA segment that contains genes for the insertion of the
DNA segment into the chromosome and for mobilization of the element
to other locations on the chromosomes.
transverse torus: See
superior mandibular torus or inferior mandibular torus.
transversion mutation:
A specific type of base-pair substitution mutation that involves
a change in the DNA from a purine-pyrimidine base pair to a pyrimidine-purine
base pair at the same site (e.g., At to TA or GC to TA).
trapezius muscle: A
muscle extending from the nuchal plane to the clavicle and scapula
that stabilizes the shoulder and brings the scapula upwards.
travertine: A calcium
carbonate rock deposited around lime-rich springs and lakes.
tribes: A term used
to describe a social grouping generally larger than a band, but
rarely outnumbering more than a few thousand; unlike bands, tribes
are usually settled farmers, though they also include nomadic pastoral
groups whose economy is based on exploitation of livestock. Individual
communities tend to be integrated into the larger society through
kinship ties.
trihybrid cross: A
cross between individuals of the same type that are heterozygous
for three pairs of alleles at three different loci.
trisomy: An aberrant,
aneuploid state in a normally diploid cell or organism in which
there are three copies of a particular chromosome instead of two
copies.
trisomy-21: A human
clinical condition characterized by various abnormalities. It is
caused by the presence of an extra copy of chromosome 21.
trochanter: A larger
process, for muscle attachment.
trochlea: Any smooth,
saddle-shaped bony surface that forms part of a joint.
trochlear (sigmoid)
notch: The notch within the hook-like proximal end of the ulna that
slides in and out of the olecranon fossa of the humerus.
true-breeding (pure-breeding)
strain: A strain allowed to self-fertilize for many generations
to ensure that the traits to be studied are inherited and unchanging.
true reversion: A point
mutation from mutant back to wild type in which the change codes
for the original amino acid of the wild type.
tubercle: A small eminence.
tuff: A consolidated
deposit of volcanic ash, transported to the site by air or more
often water.
tumor viruses: Viruses
that induce cells to dedifferentiate and to divide to produce a
tumor.
Turner syndrome: A
human clinical syndrome that results from monosomy for the X chromosome
in the female, which gives a 45,X female. These females fail to
develop secondary sexual characteristics, tend to be short, have
weblike necks, have poorly developed breasts, are usually infertile,
and exhibit mental deficiencies.
twin spots: Two adjacent
cell groups that differ in genotype and phenotype. They result from
mitotic crossing-over within the somatic cells of a heterozygous
individual.
tympanic bone: The
portion of the temporal bone that encloses the inner ear.
tympanic crest: See
petrosal crest.
tympanic membrane:
Eardrum.
type: (1) A complete
or incomplete specimen which serves as the base for the name of
a taxon; (2) a single individual used to epitomize a sample.
typology: A scheme
to order multiple types in relational manner. A common typology
orders types in a hierarchical manner.
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