Molecular Biology of the Cell by Bruce Alberts, Alexander Johnson, Julian Lewis, David Morgan, Martin Raff, Keith Roberts, Peter Walter by by Bruce Alberts, Alexander Johnson, Julian Lewis, David Morg

G:10 Glossary
Extensive methylation of the cytosine base in CG sequences
is used in plants and animals to help keep genes in an inactive
state.
DNA microarray A large array of short DNA molecules
(each of known sequence) bound to a glass microscope
slide or other suitable support. Used to monitor expression of
thousands of genes simultaneously: mRNA isolated from test
cells is converted to cDNA, which in turn is hybridized to the
microarray. (Figure 8–64)
DNA polymerase Enzyme that synthesizes DNA by joining
nucleotides together using a DNA template as a guide.
DNA primase Enzyme that synthesizes a short strand of RNA
on a DNA template, producing a primer for DNA synthesis.
(Figure 5–10)
DNA repair A set of processes for repairing the many
accidental lesions that occur continually in DNA.
DNA replication Process by which a copy of a DNA molecule
is made.
DNA supercoiling A conformation with loops or coils that
DNA adopts in response to superhelical tension; conversely,
creating various loops or coils in the helix can create such
tension.
DNA topoisomerase (topoisomerase) Enzyme that binds
to DNA and reversibly breaks a phosphodiester bond in one
or both strands. Topoisomerase I creates transient singlestrand
breaks, allowing the double helix to swivel and relieving
superhelical tension. Topoisomerase II creates transient doublestrand
breaks, allowing one double helix to pass through
another and thus resolving tangles. (Figures 5–21 and 5–22)
DNA tumor virus General term for a variety of different DNA
viruses that can cause tumors.
DNA-only transposon Transposable element that exists as
DNA throughout its life cycle. Many move by cut-and-paste
transposition. See also transposon.
dolichol Isoprenoid lipid molecule that anchors the precursor
oligosaccharide in the endoplasmic reticulum membrane during
protein glycosylation.
domain (protein domain) Portion of a protein that has
a tertiary structure of its own. Larger proteins are generally
composed of several domains, each connected to the next
by short flexible regions of polypeptide chain. Homologous
domains are recognized in many different proteins.
Dorsal protein Transcription regulator of the NFκB family
regulating gene expression and involved in establishing the
dorsoventral axis in the embryo.
double helix The three-dimensional structure of DNA, in
which two antiparallel DNA chains, held together by hydrogenbonding
between the bases, are wound into a helix.
(Figure 4–5)
drivers Mutations that are causal factors in the development
of cancer.
dynamic instability Sudden conversion from growth to
shrinkage, and vice versa, in a protein filament such as a
microtubule or actin filament. (Panel 16–2, pp. 902–903)
dynamin Cytosolic GTPase that binds to the neck of a
clathrin-coated vesicle in the process of budding from the
membrane, and which is involved in completing vesicle
formation.
dynein Large motor protein that undergoes ATP-dependent
movement along microtubules.
E2F protein Transcription regulatory protein that switches on
many genes that encode proteins required for entry into the
S phase of the cell cycle.
early endosome Common receiving compartment with
which most endocytic vesicles fuse and where internalized
cargo is sorted either for return to the plasma membrane or for
degradation by inclusion in a late endosome.
ectoderm Embryonic epithelial tissue that is the precursor of
the epidermis and nervous system.
edema factor One of the two A subunits of anthrax toxin; an
adenylyl cyclase that catalyzes production of cAMP, leading to
ion imbalance and consequent edema in the skin or lung.
effector Bcl2 family proteins Pro-apoptotic proteins of the
intrinsic pathway of apoptosis that in response to an apoptotic
stimulus become activated and aggregate to form oligomers
in the mitochondrial outer membrane, inducing the release of
cytochrome c and other intermembrane proteins. Bax and Bak
are the main effector Bcl2 family proteins in mammalian cells.
effector cell Cell that carries out the final response or
function in a particular process. The main effector cells of the
immune system, for example, are activated lymphocytes and
phagocytes that help eliminate pathogens.
egg-polarity genes Genes in the Drosophila egg that define
the anteroposterior and dorsoventral axes of the future embryo
through the creation of landmarks (mRNA or protein) in the egg
that provide signals organizing the developmental process.
elastic fiber Extensible fiber formed by the protein elastin in
many animal connective tissues, such as in skin, blood vessels,
and lungs, which gives them their stretchability and resilience.
elastin Extracellular protein that forms extensible fibers
(elastic fibers) in connective tissues.
electrochemical gradient Combined influence of a
difference in the concentration of an ion on two sides of a
membrane and the electrical charge difference across the
membrane (membrane potential). Ions or charged molecules
can move passively only down their electrochemical gradient.
electron microscope Microscope that uses a beam of
electrons to create the image.
electron microscope (EM) tomography Technique
for viewing three-dimensional specimens in the electron
microscope in which multiple views are taken from different
directions by tilting the specimen holder. The views are
combined computationally to give a three-dimensional image.
electron-transport chain Series of reactions in which
electron carrier molecules pass electrons “down the chain”
from higher to successively lower energy levels. The energy
released during such electron movement can be used to power
various processes. Electron-transport chains present in the
inner mitochondrial membrane (called the respiratory chain)
and in the thylakoid membrane of chloroplasts generate a
proton gradient across the membrane that is used to drive ATP
synthesis. See especially Figures 14–18 and 14–52.
electrostatic attraction A noncovalent, ionic bond between
two molecules carrying groups of opposite charge.
(Panel 2–3, pp. 94–95)
embryonic stem cells (ES cells) Cells derived from the
inner cell mass of the early mammalian embryo. Capable of