Biotechnology

part of the amino acid sequences (known as
the “domain”) of two or more proteins.
Formed by fusing the two protein-encoding
genes (which causes the ribosome to subse-
quently produce the fusion protein). This
fusion is often done deliberately, either to
put the expression of one of the (fused) genes
under the control of the strong promoter for
the first gene, or to allow the gene of interest
(which is difficult to assay) to be more easily
studied via substituting some of the (gene)
protein with a more easily measured
(assayed) function. For example, by fusing
a difficult-to-study gene with the 
β-galactosi-
dase gene, the (protein) product that results
can easily be measured (assayed) using chro-
matography. See also 
PROTEIN
,
AMINO ACID
,
SEQUENCE
  (
OF A PROTEIN MOLECULE
),
GENE
,
R I B O S O M E S
,
P R O M O T E R
,
A S S A Y
,
C O D I N G
SEQUENCE
,
DOMAIN
  (
OF A PROTEIN
),
GENE
FUSION
.
Fusion Toxin A fusion protein that consists of
a toxic protein (domain) plus a cell receptor
binding region (protein domain). The cell
receptor portion (of the total fusion toxin
molecule) delivers the toxin directly to the
(diseased) cell, thus sparing other healthy
tissues from the effect of the toxin. See also
FUSION PROTEIN
,
TOXIN
,
RICIN
,
PROTEIN
,
PROTEIN
ENGINEERING
,
DOMAIN
  (
OF A PROTEIN
),
RECEP-
TORS
,
ENDOCYTOSIS
.
Fusogenic Agent Any compound, virus, etc.,
that causes cells to fuse together. For exam-
ple, one of the effects of the HIV (i.e., AIDS-
causing) viruses is to cause the T cells of the
© 2002 by CRC Press LLC

F
human immune system to fuse (causing col-
lapse of the immune system). See also
ACQUIRED IMMUNE DEFICIENCY SYNDROME
(
AIDS
),
HUMAN IMMUNODEFICIENCY VIRUS TYPE
1
(
HIV-
1
),
HUMAN IMMUNODEFICIENCY VIRUS
TYPE
2
  (
HIV-
2
),
HELPER T CELLS
  (
T
4
CELLS
),
ADHESION MOLECULE
.
Futile Cycle An enzyme-catalyzed set of cyclic
reactions that results in release of thermal
energy (heat) through the hydrolysis of ATP
(adenosine triphosphate). The hydrolysis of
ATP is normally coupled to other cycles and
reactions in which the energy released is
metabolically used. However, futile cycles
would appear to waste the energy of ATP as
heat, except when one is shivering to keep
warm. The production of heat by shivering
is an example of the futile cycle. See also
ADENOSINE TRIPHOSPHATE
  (
ATP
),
ENZYME
,
HYDROLYSIS
.
© 2002 by CRC Press LLC

0-8493-XXXX-X/01/$0.00+$1.50
© 2001 by CRC Press LLC
G
G
G- See
GRAM
-
NEGATIVE
 (
G-
).
G+ See
GRAM
-
POSITIVE
 (
G
+
).
G-Protein-coupled Receptors See
G
-
PROTEINS
.
G Proteins See
G
-
PROTEINS
.
G-Proteins (Guanyl-Nucleotide Binding Pro-
teins) Discovered by Rodbell and co-workers
at America’s National Institutes of Health
(NIH), and Alfred G. Gilman and co-workers
at the American University of Virginia-Char-
lottesville, during the 1970s–1980s. These are
proteins embedded in the surface membrane
of cells. G-proteins “receive chemical sig-
nals” from outside the cell (e.g., hormones)
and “pass the signal” into the cell, so that cell
can “respond to the signal.” For example, a
hormone, drug, neurotransmitter, or other
“signal” binds to a receptor molecule on the
surface of the cell’s exterior membrane. That
receptor then activates the G-protein, which
causes an effector inside cell to produce a
second “signal” chemical inside the cell,
which causes the cell to react to the original
external chemical signal. The G-proteins are
called thus, because they become GTP and
GDP forms alternately, as part of their reac-
tion cycle (i.e., in “passing the signal”). Dys-
function of G-proteins in humans causes the
salt and water losses inherent in cholera (the
body’s compromised immune defense inher-
ent in pertussis), and is believed responsible
for some symptoms of diabetes and alcohol-
ism. Dysfunction of G-proteins in plants
causes rapid water loss (wilting). See also
PROTEIN
,
SIGNALING
,
SIGNAL TRANSDUCTION
,
HOR-
MONE
,
CELL
,
BETA CELLS
,
GTP
ases
,
GPA
1
,
INSULIN
,
RECEPTORS
,
NATIONAL INSTITUTES OF HEALTH
(
NIH
),
NEUROTRANSMITTERS
,
TRANSMEMBRANE
PROTEINS
,
ION CHANNELS
,
CHOLERA TOXIN
.
GA21 A naturally occurring gene (i.e.,
expressed at low levels in some plants)
which confers resistance to glyphosate-con-
taining herbicides. When the GA21 gene is
inserted by man into crop plants (e.g.,
maize/corn) in a way that causes high
expression, those crop plants are subse-
quently unaffected when glyphosate-con-
taining herbicides are applied to fields to
cotnrol weeds in those crops. See also 
GENE
,
EXPRESS
,
EXPRESSIVITY
,
PROTEIN
,
GENETIC ENGI-
NEERING
,
CORN
,
HERBICIDE
-
TOLERANT CROP
,
GLYPHOSATE
.
Galactose (gal) A monosaccharide occurring
in both levo (
L
) and dextro (
D
) forms as a
constituent of plant and animal oligosaccha-
rides (lactose and raffinose) and polysaccha-
rides (agar and pectin). Galactose is also
known as cerebrose. See also 
STEREOISOMERS
,
DEXTROROTARY
  (
D
)
ISOMER
,
LEVOROTARY
  (
L
)
ISOMER
.
Gall See
T
i
PLASMID
.
GalNAc N-acetyl-
D
-galactosamine.
GALT See
GUT
-
ASSOCIATED LYMPHOID TISSUE
.
Gamete A germ or reproductive cell. In ani-
mals (and humans) the functional, mature,
male gamete is called a spermatozoon; in
plants it is called a spermatozoid. In both
animals and plants the female gamete is
called the ovum, or egg. See also 
OOCYTES
.
Gamma Globulin A type of blood protein that
plays a major role in the process of immunity
(immune system response). Sometimes the
term “gamma globulin” refers to a whole
group of blood proteins that are known as
antibodies or immunoglobulins (Ig). Most
often, however, it applies to a particular
immunoglobulin, designated as IgG,
believed to be the most abundant type of
antibody in the body. See also 
ANTIBODY
,
G GUT
-
ASSOCIATED LYMPHOID TISSUE
  (
GALT
),
PROTEIN
,
IMMUNOGLOBULIN
.
© 2002 by CRC Press LLC

G
Gamma Interferon Produced by T lympho-
cytes. See also 
INTERFERONS
,
T LYMPHOCYTES
.
GAP A double-stranded DNA is said to be
“gapped” when one strand is missing over a
short region of the molecule. See also 
DEOXY-
RIBONUCLEIC ACID
 (
DNA
).
Gated Transport (of a protein) One of three
means for a protein molecule to pass
between compartments within eucaryotic
cells. The compartment “wall” (membrane)
possesses a “sensor” (receptor) that detects
the presence of a correct protein (e.g., after
that protein has been synthesized in the cell’s
ribosomes), then opens a “gate” (pore) in the
membrane to allow that protein to pass from
the first compartment to the second compart-
ment. See also 
PROTEIN
,
EUCARYOTE
,
CELL
,
RIBOSOMES
,
SIGNALING
,
VESICULAR TRANSPORT
.
GDH Gene See
GLUTAMATE DEHYDROGENASE
.
GDNF See
GLIAL DERIVED NEUROTROPHIC FACTOR
.
GEAC The country of India’s Genetic Engi-
neering Approval Committee. The GEAC
must approve a rDNA product (e.g., a genet-
ically engineered crop plant that earlier
received its “bio safety clearance” from the
Indian Department of Biotechnology) before
that rDNA product is allowed to be commer-
cially planted. See also 
GENETIC ENGINEERING
,
r
DNA
,
INDIAN DEPARTMENT OF BIOTECHNOLOGY
.
Gel A colloid, where the dispersed phase is
liquid and the dispersion medium is solid.
Gel Electrophoresis See
TWO
-
DIMENSIONAL
 (
2
D
)
GEL ELECTROPHORESIS
,
POLYACRYLAMIDE GEL
ELECTROPHORESIS
 (
PAGE
),
ELECTROPHORESIS
.
Gel Filtration Also known as exclusion chro-
matography. An effective technique for sep-
arating molecules (such as peptide mixtures)
on the basis of size. This is accomplished by
passing a solution of the molecules to be
separated over a column of Sephadex
®
, for
example, which is a polymerized carbo-
hydrate derivative that contains tiny holes.
The holes are of such a size that some of the
smaller molecules diffuse into them and are
in this way retained (held back) while the
larger molecules are not able to get into the
holes and pass on by the solid phase (Sepha-
dex
®
, in this example). This, simplistically,
is how separation is effected. See also
ELECTROPHORESIS
,
CHROMATOGRAPHY
,
FIELD
INVERSION GEL ELECTROPHORESIS
.
GEM (Germ plasm Enhancement for
Maize) A project conducted under the aus-
pices of the U.S. Department of Agriculture,
in concert with 16 American universities and
20 corn (maize) seed companies. GEM’s
intent is to cross exotic (not in current use)
germ plasm with commercial maize lines in
order to increase corn yield. See also 
CORN
,
GERM PLASM
,
HYBRIDIZATION
 (
PLANT GENETICS
),
PLEIOTROPIC
.
GEMP (Genetically Engineered Microbial
Pesticide) See
GENETICALLY ENGINEERED
MICROBIAL PESTICIDE
,
INTEGRATED PEST MAN-
AGEMENT
 (
IPM
).
Gene A natural unit of the hereditary material,
which is the physical basis for the transmis-
sion of the characteristics of living organisms
from one generation to another. The basic
genetic material is fundamentally the same
in all living organisms: it consists of chain-
like molecules of nucleic acids — deoxyribo-
nucleic acid (DNA) in most organisms and
ribonucleic acid (RNA) in certain viruses —
and is usually associated in a linear arrange-
ment that (in part) constitutes a chromosome.
The segment of DNA that is involved in
producing a polypeptide chain. It includes
regions preceding and following the coding
region (leader and trailer) as well as inter-
vening sequences (introns) between individ-
ual coding segments (exons). More than one
protein can be expressed (made) from a
given gene (i.e., the particular protein
expressed is determined by factors such as
the cell’s temperature or other environmental
variable, or the presence of STATs, some of
which themselves are proteins). See also
INFORMATIONAL MOLECULES
,
DEOXYRIBO-
NUCLEIC ACID
  (
DNA
),
RIBONUCLEIC ACID
  (
RNA
),
GENE EXPRESSION
,
CHROMOSOMES
,
EXPRESS
,
MESSENGER RNA
 (
m
RNA
),
CODON
,
INTRON
,
EXON
,
CODING SEQUENCE
,
GENE EXPRESSION CASCADE
,
CENTRAL DOGMA
  (
NEW
),
SIGNAL TRANSDUCERS
AND ACTIVATORS OF TRANSCRIPTION
 (
STAT
s
).
Gene “Stacking” See “
STACKED
”
GENES
.
Gene Amplification The copying of segments
(e.g., genes) within the DNA or RNA
molecule. This can be done by man (e.g.,
© 2002 by CRC Press LLC

G
polymerase chain reaction), can be caused
by certain chemical carcinogens (e.g., phor-
bol ester), or occur naturally (e.g., in pro-
caryotes and certain lower eucaryotes). The
five primary techniques used by man to per-
form gene amplification are:
1. Polymerase Chain Reaction (PCR)
2. Ligase Chain Reaction (LCR)
3. Self-sustained Sequence Replication
(SSR)
4. Q-beta Replicase Technique
5. Strand Displacement Amplification
(SDA) 
See also 
GENE
,
Q
-
BETA REPLICASE TECHNIQUE
,
POLYMERASE CHAIN REACTION
 (
PCR
),
CARCINOGEN
,
PROCARYOTE
,
EUCARYOTE
.
Gene Array Systems See
BIOCHIPS
,
PROTEOM-
ICS
,
GENE EXPRESSION ANALYSIS
.
Gene Chips See
BIOCHIPS
,
GENE EXPRESSION
ANALYSIS
,
PROTEOMICS
.
Gene Delivery (gene therapy) The insertion of
genes (e.g., via retroviral vectors) into
selected cells in the body in order to:
1. cause those cells to produce specific
therapeutic agents (growth hormone in
livestock, factor VIII in hemophiliacs,
insulin in diabetics, etc.). A potential
way of curing some genetic diseases, in
that the inserted gene will produce the
protein and/or enzyme that is missing in
the body due to a defective gene (thus
causing the genetic disease). Approxi-
mately 3,000 genetic diseases are known
to man. Examples of genetic diseases
include cystic fibrosis, sickle cell ane-
mia, Huntington’s disease, phenylketo-
nuria (PKU), Tay-Sach’s disease, ADA
deficiency (adenosine deaminase
enzyme deficiency), and thalassemia.
2. cause those cells to become (more)
susceptible to a conventional therapeu-
tic agent that previously was ineffec-
t i v e   a g a i n s t   t h a t   p a r t i c u l a r
condition/disease (e.g., insertion of Hs-
tk gene into brain tumor cells to make
those tumor cells susceptible to the
Syntex drug Ganciclovir).
3. cause those cells to become less sus-
ceptible to a conventional therapeutic
agent (e.g., insert genes into healthy
tissue in order to enable that healthy
tissue to resist the harmful effects of
such conventional chemotherapy agents
as vincristine).
4. counter the effects of abnormal (dam-
aged) tumor suppressor genes via inser-
tion of normal tumor suppressor genes.
5. cause expression of ribozymes that
cleave oncogenes (cancer-causing
genes).
6. be used for other therapeutic uses of
genes in cells.
See also 
TUMOR SUPPRESSOR GENES
,
ONCOGENES
,
CANCER
,
p53
GENE
,
TUMOR
,
PROTO
-
ONCOGENES
,
RETROVIRAL VECTORS
,
RETROVIRUSES
,
HUNTING-
TON
’
S DISEASE
,
GENETIC CODE
,
INFORMATIONAL
MOLECULES
,
DEOXYRIBONUCLEIC ACID
  (
DNA
),
CHROMOSOMES
,
HORMONE
,
ENZYME
,
PROTEIN
,
GENETIC TARGETING
.
Gene Expression Conversion of the genetic
information within a gene, into an actual
protein (or cell process). Note that many
genes are only expressed at specific times
during the lifetime of an organism. Some
genes are expressed in a “cascade” of related
expressions. See also 
GENE
,
GENETIC CODE
,
INFORMATIONAL MOLECULES
,
EXPRESS
,
GENE
EXPRESSION ANALYSIS
,
BIOCHIPS
,
GENE EXPRES-
SION CASCADE
,
CENTRAL DOGMA
 (
NEW
).
Gene Expression Analysis Generally done
via use of “biochips” (which have numerous
detection/analysis devices fabricated onto
their silicon surface) or “microarrays,” gene
expression analysis involves evaluation of
the expression (and expression levels) of
numerous genes in a biological sample, to
analyze/compare any differences between
gene expression/products in:
1. Normal cells vs. diseased cells.
2. Normal cells vs. those responding to a
stimulus.
3. Cells from the same organism, at dif-
ferent stages of development (e.g.,
embryo versus adult).
© 2002 by CRC Press LLC

G
4. Normal (historic wild type) cells vs.
genetically engineered cells (those that
have been engineered to cure a disease,
resist an herbicide, etc.).
5. normal cells vs. those same cells treated
with a given pharmaceutical (candidate).
Analysis generally involves measurement
of gene expression markers (i.e., molecules
synthesized, or cellular consequences such
as apoptosis) to determine which genes are
expressed (and when/how much, etc.). See
also
GENE
,
GENE EXPRESSION
,
GENE EXPRESSION
PROFILING
,
MICROARRAY
  (
TESTING
),
GENOMICS
,
FUNCTIONAL GENOMICS
,
EXPRESS
,
EXPRESSED
SEQUENCE TAGS
  (
EST
),
ZINC FINGER PROTEINS
,
BIOCHIPS
,
HIGH
-
THROUGHPUT SCREENING
  (
HTS
),
MICROFLUIDICS
,
HERBICIDE
-
TOLERANT CROP
,
GENE DELIVERY
  (
GENE THERAPY
),
HORMONE
,
PROTEOMICS
,
PROMOTER
,
GENE EXPRESSION
MARKERS
,
GENE EXPRESSION CASCADE
,
APOPTOSIS
,
RT
-
PCR
.
Gene Expression Cascade A sequential series
of individual gene expressions (i.e., each
gene causing a separate/different protein to
be “manufactured”), that is initiated (“set
off”) by the first gene expression. For exam-
ple, a gene expression cascade is often ini-
tiated by the first gene causing expression of
a transcription factor (i.e., protein that itself
interacts with cell’s DNA to either cause or
speed up yet another gene expression). The
protein resulting from that second gene
expression could be yet another transcription
factor that triggers another (i.e., third) gene
expression, and so on. See also 
GENE
,
EXPRESS
,
GENE EXPRESSION
,
CASCADE
,
PROTEIN
,
CELL
,
DEOXYRIBONUCLEIC ACID
 (
DNA
),
PROMOTER
,
TRANSCRIPTION FACTORS
,
APOPTOSIS
.
Gene Expression Markers Refers to mole-
cules (e.g., synthesized due to a specific
gene’s expression) or consequences (e.g., cell
apoptosis due to a specific gene’s expression)
that can be measured as proof of gene’s
expression in gene expression analysis. See
also
GENE EXPRESSION
,
GENE
,
GENE EXPRESSION
ANALYSIS
,
EXPRESS
,
BIOCHIPS
,
PROTEIN
,
CELL
,
APOPTOSIS
,
GREEN FLUORESCENT PROTEIN
.
Gene Expression Profiling Determination of
specifically which genes are “switched on”
(e.g., in a cell), thereby enabling precise
definition of the phenotypic condition of that
cell (i.e., the phenotype of that cell at that
moment). Typical uses (i.e., comparison of
such tissue phenotypes) include:
1. Comparing diseased cell with normal
cell.
2. Defining quantitatively the “normal”
state.
3. Comparing a given drug’s impact (i.e.,
treated cell with normal cell).
4. Comparing old cell with young cell.
In subsequent gene expression analysis, the
quantitative amounts of each protein being
expressed can be determined via use of such
technologies as two-dimensional (2D) gel
electrophoresis, Southern blot analysis, flu-
orescence tagging, radiolabeling, RT-PCR,
QPCR, plane polarimetry, etc. See also 
GENE
,
GENE EXPRESSION
,
PROTEIN
,
CELL
,
PHENOTYPE
,
GENE EXPRESSION ANALYSIS
,
TWO
-
DIMENSIONAL
(
2
D
)
GEL ELECTROPHORESIS
,
SOUTHERN BLOT
ANALYSIS
,
RADIOLABELED
,
RT
-
PCR
,
QPCR
,
GENE
EXPRESSION MARKERS
,
MICROARRAY
 (
TESTING
).
Gene Function Analysis The determination
of which protein is expressed (i.e., caused to
be “manufactured”) by each gene in an
organism’s genome/DNA. Typically, gene
function analysis follows after discovery of
gene sequences found via structural genom-
ics study. Some methods utilized to deter-
mine which proteins result from which
gene(s) are:
1. Site-directed mutagenesis (SDM) to
compare two same-species organisms
possessing two different genes at the
same site (SNP) on the genome (i.e.,
on organism’s DNA).
2. Antisense DNA sequences to compare
two same-species organisms, one of
which has a gene at the same site
“turned off” (silenced) via antisense
DNA.
3. Reporter gene, to compare two same-
species organisms (possessing two dif-
ferent genes at the same site on
genome/DNA) via a reporter gene
adjacent to the gene/site, to detect
© 2002 by CRC Press LLC

G
presence or absence of the desired
trait/function.
4. Comparison of same organism (e.g.,
crop plant) when one of the two is “chal-
lenged” by a specific plant disease.
5. Chemical genetics, to compare two
same-species organisms (one of which
has gene at the specific site at least
partially inactivated by a specific
chemical).
6. “Silencing” or “knocking out” a partic-
ular gene via other methods than anti-
sense or chemical genetics, to compare.
7. Use of already-known “model organ-
isms” (e.g., Drosophila for comparing
insect genes, Arabidopsis thaliana for
plant genes, Caenorhabditis elegans
for animal genes).
See also 
GENE
,
GENE EXPRESSION
,
GENETIC
CODE
,
INFORMATIONAL MOLECULES
,
EXPRESS
,
PROTEIN
,
GENOME
,
GENOMICS
,
STRUCTURAL
GENOMICS
,
FUNCTIONAL GENOMICS
,
ZINC FINGER
PROTEINS
,
TRAIT
,
DEOXYRIBONUCLEIC ACID
(
DNA
),
SEQUENCE
 (
OF A DNA MOLECULE
),
POINT
MUTATION
,
SITE
-
DIRECTED MUTAGENESIS
  (
SDM
),
ANTISENSE
  (
DNA SEQUENCE
),
GENE SILENCING
,
REPORTER GENE
,
METHYLATION
,
POSITIONAL
CLONING
,
DNA METHYLATION
,
CHEMICAL GENETICS
,
MODEL ORGANISM
,
DROSOPHILA
,
ARABIDOPSIS
T H A L I A N A
,
C A E N O R H A B D I T I S
E L E G A N S
(
C
.
ELEGANS
),
CENTRAL DOGMA
  (
OLD
),
CENTRAL
DOGMA
  (
NEW
),
TRANSCRIPTION FACTORS
,
TRAN-
SWITCH
®
,
SINGLE
-
NUCLEOTIDE POLYMORPHISMS
(
SNP
s
).