the nerve impulse will be transmitted. The
response is achieved by making the postsynaptic
neuron more negatively charged by opening
chloride channels. (5.2)initiation the first step in transcription, in which
the position along the original DNA strand where
transcription is to begin is determined. (8.2)
Also, in translation, the name given to the first
step, in which a special initiator tRNA molecule
binds to a ribosome-mRNA complex to begin
translation. (8.3)
inorganic term generally used to describe
substances that do not contain carbon, such as
water and sodium chloride. (1.2)
in situtherapy in gene therapy, injecting the vector
directly into the tissue containing target cells.
For example, a vector containing a gene that
combats cancer can be injected directly into a
tumour. (9.4)
insulin hormone that is produced in the islets of
Langerhans in the pancreas and that lowers
blood sugar levels. (4.3)
integrator in the nervous system, describes the
function of the hypothalamus in the brain that
receives messages from receptors and sends
instructions to effectors. (4.1)
interspecific competition competition between
or among members of different species for
resources, such as food. (14.3)
interstitial cells cells surrounding the seminiferous
tubules in the testes. (6.3)
interstitial fluid fluid in the pores between cells.
(4.1)
intraspecific competition competition between
or among members of the same species for
resources, such as food. (14.3)
intron intervening non-coding sequence in a
eukaryote gene. (7.4)
in vivotherapy in gene therapy, a process that
relies on a vector that can be taken up by the
body through injection or inhalation. Once inside
the body, the vector targets specific cells and
inserts new genes directly into these cells. So far,
these treatments have been unsuccessful. (9.4)
ion charged particle formed when an atom loses or
gains electrons, so that the atom does not have an
equal number of protons or electrons. (1.1)
ionic bond chemical bond formed by the transfer
of electrons between atoms and the attraction
between the oppositely charged ions that result.
(1.1)
iris the muscle that adjusts the pupil to regulate the
amount of light that enters the eye. (5.3)
islets of Langerhans groups of cells in the pancreas
that produce insulin and glucagon. (4.3)
isomers two or more molecules with the same
molecular formula but different structures. (1.2)
isotonic two solutions (usually, on either side of a
membrane) that have the same concentrations of
solutes and water. (4.2)
isotopes atoms of the same element that have
different numbers of neutrons in their nuclei.
(1.1)J-shaped curve the shape of a line describing
exponential growth of a population. (14.2)kidney organ that filters blood to remove
nitrogenous wastes and adjust the concentrations
of salts in the blood. (4.2)
kinetic energy the energy associated with
movement. (2.1)
K-selection the type of selection at work in
populations at their carrying capacities, in which
individuals have few, large offspring and care for
them. (14.4)
Krebs cycle metabolic pathway consisting of a
series that completes the breakdown of glucose
in the mitochondrion. (3.1)lagging strand in DNA replication, the strand that is
replicated by splicing together Okazaki fragments
in the 5 ′to 3 ′direction (in the direction opposite
to the movement of the replication fork). (7.3)
laws of thermodynamics set of laws governing the
relationship between heat and other forms of
energy. For example, the first law states that
energy can be neither created nor destroyed, but
can be transformed from one form of energy to
another. The second law states that energy
cannot be transformed from one form to another
without a loss of energy. In other words, every
energy transformation increases the total entropy
of the universe. (2.1)
leading strand in DNA replication, the strand that
is replicated continuously in the 5 ′to 3 ′direction
(in the same direction as the movement of the
replication fork). (7.3)
lens the clear, flexible part of the eye that adjusts its
shape according to focal distance. (5.3)
less industrialized nation country with relatively
few industries and a relatively low standard of
living, compared to more industrialized nations.
(15.1)
life history schedule of certain important events
that occur during the life of an organism (e.g., age
of sexual maturity). (14.4)L
K
J
Glossary • MHR 579