Encyclopedia of Biology

trapping The interception of a reactive molecule or
reaction intermediate so that it is removed from the
system or converted into a more STABLEform for study
or identification.

tree Aperennial plant that grows from the ground
up, usually with a single, mostly tall, woody, self-
supporting trunk or stem with bark, and an associated
elevated crown of branches and foliage. May shed
leaves or keep needles yearly.

trench fever A bacterial infection that causes
repeated cycles of high fever. Common in World War
I and II, due to bacteria that was passed among
soldiers through contact with body lice, overcrowd-
ing, and bad hygiene conditions among soldiers in

trenches. Two different bacteria can cause trench

fever: Bartonella quintanaand Bartonella henselae.

B.quintanaiscarried by body lice; B. henselaeis

carried by ticks.

Triassic The earliest period of the Mesozoic era (248

million to 213 million years ago).

See alsoGEOLOGICAL TIME.

trichinosis A disease caused by the roundworm

(nematode) Trichinella spiralis. Caused by eating

unprepared or improperly cooked meats, particularly

pork products.

trichocyst A structure in the outer cytoplasm of cili-

ates and dinoflaggelates that produces hairlike or dart-

like fibers that can be discharged for defensive/

offensive purposes in organisms, e.g., paramecium.

trilobite Ancient class (Trilobita) of hard-shelled,

segmented creatures with jointed legs; one of the first

arthropods, they existed over 300 million years ago in

the Earth’s ancient seas. There arenine orders, more

than 150 families, 5,000 genera, and over 15,000

described species. Mostly detritivores, predators, or

scavengers, the trilobites were one of the most diverse

groups ever known.

triplet code Acode in which a given amino acid is

specified by a set of three nucleotides (codons).

See alsoCODON.

triploblastic Organisms formed with three cell lay-

ers, the endoderm, mesoderm, and ectoderm.

triploidy A rare chromosomal abnormality where

three complete sets of the haploid genome exist instead

of the normal two sets. In humans there are 69

chromosomes instead of the normal 46 chromosomes.

Usually results in miscarriage or death in the first few

hours or days after birth.

triploidy 329

derivative

chromosome

20

Before translocation After translocation

chromosome

4

derivative

chromosome

4

chromosome

20

Translocation involves the breakage and removal of a large seg-
ment of DNA from one chromosome, followed by the segment’s
attachment to a different chromosome.(Courtesy of Darryl Leja,
NHGRI, National Institutes of Health)