Biotechnology

Allele From the Greek allelon, mutually each
other, the term refers to one of several alter-
nate forms of a gene occupying a given locus
on the chromosome, which controls expres-
sion (of product) in different ways. See also
EXPRESS
,
GENE
,
CHROMOSOMES
,
LOCUS
.
Allelic Exclusion The expression in any par-
ticular manner of only one of the alleles in
an antibody gene within a B lymphocyte
(cell), coding for the expressed antibody. See
also
A L L E L E
,
C O D I N G
S E Q U E N C E
,
G E N E
,
B LYMPHOCYTES
,
ANTIBODY
,
IMMUNOGLOBULIN
.
© 2002 by CRC Press LLC

A
Allelopathy Refers to the secretion of certain
chemicals (e.g., terpenoid compounds) by a
plant, in order to hinder the growth or repro-
duction of other plants growing near it.
Allergies (airborne) See
MAST CELLS
.
Allergies (foodborne) A n   I g E - m e d i a t e d
(aggressive) immune system response to
antigen(s) present on protein molecules in
the particular food to which (a given) person
is allergic. The antibodies (IgE) bind to those
antigens and trigger a humoral immune
response that can cause vomiting, diarrhea,
skin reactions, wheezing, and respiratory
distress. In severe cases, the immune
response can cause death. In some rare
instances, the allergic reaction is mediated
by sensitized T cells. In some rare instances,
the onset of a food allergy incident is
induced by exercise (before or after eating
that particular food).
The U.S. Food and Drug Administration
(FDA) requires testing in advance to deter-
mine if a genetically engineered foodstuff
has the potential to cause allergic reactions
in humans, before that genetically engi-
neered foodstuff (e.g., a modified crop plant)
is approved by the FDA. In general, known
food allergens (e.g., peanuts, Brazil nuts,
wheat, etc.) are protein molecules that are
resistant to rapid digestion (because those
protein molecules are too tightly “folded
together” for digestive enzymes to access
their chemical bonds to break down). One
potential way to genetically engineer cur-
rently allergenic crops (e.g., wheat) to make
them less allergenic, is to insert gene(s) for
extra production of thioredoxin. Found in all
living organisms, thioredoxin is a protein
that targets and breaks down the chemical
bonds holding together a tightly folded-
together protein molecule (thereby making
those protein molecules easier to digest).
Future crops engineered to contain more
thioredoxin than the traditional average level
may be nonallergenic. See also 
PROTEIN
,
PRO-
TEIN FOLDING
,
ANTIBODY
,
ANTIGEN
,
FOOD AND
DRUG ADMINISTRATION
 (
FDA
),
GENETIC ENGINEER-
ING
,
IMMUNOGLOBULIN
,
HUMORAL IMMUNITY
,
MAST CELLS
,
LEUKOTRIENES
,
DIGESTION
 (
WITHIN
ORGANISMS
),
ORGANISM
.
Allicin See
ALICIN
.
Allogeneic With a different set of genes (but
same species). For example, an organ trans-
plant from one nonrelated human to another
is allogeneic. An organ transplant from a
baboon to a human would be xenogeneic.
See also 
GENE
,
SPECIES
,
XENOGENEIC ORGANS
.
Allosteric Enzymes R eg u l a t o r y   e n z y m e s
whose catalytic activity is modulated by the
noncovalent binding of a specific metabolite
(effector) at a site (regulatory site) other than
the catalytic site (on the enzyme). Effector
binding causes a three-dimensional confor-
mation change in the enzyme and is the root
of the modulation. The term allosteric is used
to differentiate this form of regulation from
the type that may result from the competition
between substrate and inhibitors at the cata-
lytic site. See also 
ENZYME
,
STERIC HINDRANCE
,
EFFECTOR
,
CONFORMATION
,
ACTIVE SITE
.
Allosteric Site The site on an (allosteric)
enzyme molecule where, via noncovalent
binding to the site, a given effector can
increase or decrease that enzyme’s catalytic
activity. Such an effector is called an allos-
teric effector because it binds at a site on the
enzyme molecule that is other (allo) than the
enzyme’s catalytic site. See also 
ALLOSTERIC
ENZYMES
,
ACTIVATOR
,
CATALYTIC SITE
,
EFFEC-
TOR
,
CONFORMATION
,
ENZYME
,
METABOLITE
,
CATALYST
.
Allotypic Monoclonal Antibodies Monoclonal
antibodies that are isoantigenic. See also
MONOCLONAL ANTIBODIES
 (
MA
b
),
ANTIGEN
.
Allozyme See
ALLOSTERIC ENZYMES
.
Aloe vera L. A plant whose sap (juice) con-
tains certain carbohydrates that naturally
assist healing of human skin (wounds).
Those carbohydrates “activate” macroph-
ages, which cause those macrophages to pro-
duce cytokines (that regulate human immune
system and inflammatory responses which
promote healing). See also 
PHYTOCHEMICALS
,
CARBOHYDRATES
 (
SACCHARIDES
),
MACROPHAGE
,
CYTOKINES
.
Alpha Amylase Inhibitor-1 A protein natu-
rally produced in the seeds of the plant
known as the common bean Phaseolus vul-
garis that inhibits the amylase enzyme in the
gut of the pest insect known as the pea weevil.
Because the amylase enzyme (in its gut) is
inhibited (prevented from helping digestion)
© 2002 by CRC Press LLC

A
by the Alpha Amylase Inhibitor-1, the seeds
of the P. vulgaris plant are protected from
depradation by the pea weevil. See also 
PRO-
TEIN
,
ENZYME
,
AMYLASE
,
WEEVILS
.
Alpha Galactosides Term referring to a fam-
ily of polysaccharides (produced in plant
seeds) composed (at the molecular level) of
one sucrose unit linked by a 1,6 molecular
bond to several galactose units. Alpha galac-
tosides include raffinose, stachyose, and ver-
bascose. See also 
P O L Y S A C C H A R I D E S
,
GALACTOSE
 (
GAL
),
STACHYOSE
.
Alpha Helix (
␣-helix) A highly regular (i.e.,
repeating) structural feature that occurs in
certain large molecules. First discovered in
protein molecules by Linus Pauling in the
late 1940s. See also 
A
-
DNA
,
PROTEIN
,
PROTEIN
FOLDING
,
PROTEIN STRUCTURE
.
Alpha Interferon Also written as 
α-inter-
feron, it has been shown to prolong life and
reduce tumor size in patients suffering from
Kaposi’s sarcoma (a cancer that affects
approximately 10% of people with acquired
immune deficiency syndrome). It is also
effective against hairy-cell leukemia and
may work against other cancers. It has
recently been approved by the U.S. FDA for
use against certain types of sarcoma. Recent
research indicates that injections of alpha
interferon can limit the liver damage typi-
cally caused by hepatitis C, a viral disease.
See also 
INTERFERONS
.
ALS A plant enzyme (also present in some
microoganisms) known as acetolactate syn-
thase or acetohydroxy acid synthase. ALS
catalyzes (enables to occur) one of the early
chemical reaction steps in the synthesis
(manufacturing) of branched-chain amino
acids (isoleucine, leucine, valine) required by
plants to sustain life (i.e., to make needed
proteins). Herbicides that deactivate/destroy
ALS are effective at killing plants (e.g.,
weeds). See also 
ENZYME
,
GENE
,
ALS GENE
,
MICROORGANISMS
,
CATALYST
,
AMINO ACID
,
ISO-
LEUCINE
 (
ile
),
LEUCINE
 (
leu
),
VALINE
 (
val
).
ALS Gene Gene that codes for (i.e., causes to
be produced in microorganisms or plants’
chloroplasts) the critical-to-plants enzyme
acetolactate synthase (ALS). See also 
GENE
,
HTC
,
MICROORGANISMS
,
CHLOROPLASTS
,
ENZYME
,
CATALYST
,
AMINO ACID
,
ISOLEUCINE
 (
ile
),
LEUCINE
(
leu
),
VALINE
,
STS SULFONYLUREA
  (
HERBICIDE
)-
TOLERANT SOYBEANS
.
Alternative mRNA Splicing See
TRANSCRIP-
TOME
,
CENTRAL DOGMA
 (
NEW
).
Alternative Splicing See
TRANSCRIPTOME
,
CEN-
TRAL DOGMA
 (
NEW
).
Alu Family A set of dispersed and related
genetic sequences, each about 300 base pairs
long, in the human genome. At both ends of
these 300 bp segments there is an A-G-C-T
sequence. Alu 1 is a restriction enzyme that
recognizes this sequence and cleaves (cuts)
it between the G (guanine) and the
C (cytosine). See also 
GENOME
,
RESTRICTION
ENDONUCLEASES
.
Aluminum Resistance See
CITRATE SYNTHASE
(
CS
b
)
GENE
,
GENE
,
CITRIC ACID
.
Aluminum Tolerance See
CITRATE SYNTHASE
(
CS
b
)
GENE
,
GENE
,
CITRIC ACID
.
Aluminum Toxicity See
CITRATE SYNTHASE
(
CS
b
)
GENE
,
GENE
,
CITRIC ACID
.
Alzheimer’s Disease N a m e d   a f t e r  A l o i s
Alzheimer who, in 1906, first described the
Amyloid_␤_Protein_Precursor_(A_␤PP)'>Amyloid
β Protein (AβP) plaques in the
human brain that are caused by this disease.
Alzheimer’s disease causes progressive
memory loss and dementia in its victims as
it kills brain cells (neurons). Some drugs
(e.g., tacrine, donepezil, etc.) appear to slow
the progression of Alzheimer’s disease (by
increasing the availability of acetylcholine
in the brain), but there is currently no way
to stop the disease. See also 
AMYLOID
β
PRO-
TEIN
  (
A
β
P
),
AMYLOID
β
PROTEIN PRECURSOR
(
A
β
PP
),
NEURON
,
NEUROTRANSMITTER
,
ACETYL-
CHOLINE
,
OXIDATIVE STRESS
.
AMD Acronym for Age-related Macular
Degeneration. See also 
LUTEIN
.
American Society for Biotechnology (ASB)
A society founded for the purpose of “pro-
viding a multi- and interdisciplinary forum
for those persons from academia, industry,
and government who are interested in any
and all aspects of biotechnology, and will
achieve its aims by cooperation with existing
organizations active in the field.” To join,
write to ASB, P.O. Box 2820, Sausalito, Cal-
ifornia, 94966-2820. See also 
BIOTECHNOLOGY
,
INTERNATIONAL SOCIETY FOR THE ADVANCEMENT
OF BIOTECHNOLOGY
  (
ISAB
),
BIOTECHNOLOGY
INDUSTRY ORGANIZATION
 (
BIO
).
© 2002 by CRC Press LLC

A
American Type Culture Collection (ATCC)
An independent, nonprofit organization
established in 1925 for the preservation and
distribution of reference cultures. See also
CELL CULTURE
,
CULTURE
,
CULTURE MEDIUM
,
TYPE SPECIMEN
,
CONSULTATIVE GROUP ON INTER-
NATIONAL AGRICULTURAL RESEARCH
 (
CGIAR
).
Ames Test A simple bacterial-based carcino-
gens test that was developed by Bruce Ames
in 1961. Although this test evaluates
mutagenesis (causation of mutations) in the
DNA of bacteria, its results have been uti-
lized to approve or not approve certain com-
pounds for consumption by humans. See
also
BIOASSAY
,
BACTERIA
,
ASSAY
,
MUTUAL REC-
OGNITION AGREEMENTS
 (
MRA
s
),
GENOTOXIC CAR-
CINOGENS
,
CARCINOGEN
,
PARP
.
Amino Acid There are 20 common amino
acids, each specified by a different arrange-
ment of three adjacent DNA nucleotides.
These are the building blocks of proteins.
Joined together in a strictly ordered chain,
the sequence of amino acids determines the
character of each protein (chain) molecule.
The 20 common amino acids are: alanine,
arginine, aspartic acid, glutamic acid,
glutamine, glycine, histidine, isoleucine, leu-
cine, phenylalanine, proline, serine, threo-
nine, tryptophan, tyrosine, valine, cysteine,
methionine, lysine, and asparagine. Note that
virtually all of these amino acids (except gly-
cine) possess an asymmetric carbon atom,
and thus are potentially chiral in nature. See
also
PROTEIN
,
POLYPEPTIDE
 (
protein
),
STEREOISO-
MERS
,
CHIRAL COMPOUND
,
MESSENGER RNA
(
m
RNA
),
ESSENTIAL AMINO ACIDS
,
DEOXYRIBO-
NUCLEIC ACID
 (
DNA
),
ABSOLUTE CONFIGURATION
.
Amino Acid Profile Also known as “protein
quality,” this refers to a quantitative delinea-
tion of how much of each amino acid is
contained in a given source of (livestock feed
or food) protein. For example, the amino
acid profile of soybean meal is matched clos-
est to the profile of amino acids needed for
human nutrition, of all protein meals. See
also “
IDEAL PROTEIN
”
CONCEPT
,
PROTEIN
,
AMINO
ACID
,
SOYBEAN MEAL
,
PDCAAS
.
Aminocyclopropane Carboxylic Acid Syn-
thase/deaminase See
ACC SYNTHASE
,
ACC
.
AMP See
ADENOSINE MONOPHOSPHATE
 (
AMP
).
Amphibolic Pathway A metabolic pathway
used in both catabolism and anabolism. See
also
ANABOLISM
,
CATABOLISM
.
Amphipathic Molecules Molecules bearing
both polar and nonpolar domains (within the
same molecule). Some examples of amphi-
pathic molecules are wetting agents (SDS),
and membrane lipids such as lecithin. See
also
MICELLE
,
REVERSE MICELLE
 (
RM
),
POLARITY
(
CHEMICAL
).
Amphiphilic Molecules Also known collec-
tively as amphiphiles, these molecules pos-
sess distinct regions of hydrophobic (“water
hating”) and hydrophilic (“water loving”)
character within the same molecule. When
dissolved in water above a certain concentra-
tion (known as the CMC), they are capable
of forming high molecular weight aggre-
gates, or micelles. See also 
CRITICAL MICELLE
CONCENTRATION
,
HYDROPHOBIC
,
HYDROPHILIC
,
MICELLE
,
REVERSE MICELLE
 (
RM
).
Amphoteric Compound A compound capa-
ble of both donating and accepting protons
and thus able to act chemically as either an
acid or a base.
Amplicon A specific sequence of DNA pro-
duced by a DNA-amplification technology
such as the Polymerase Chain Reaction
(PCR) technique. See also 
DEOXYRIBONUCLEIC
ACID
  (
DNA
),
SEQUENCE
  (
OF A DNA MOLECULE
),
POLYMERASE CHAIN REACTION
 (
PCR
)
TECHNIQUE
,
NESTED PCR
.
Amplification The production of additional
copies of a chromosomal sequence, found as
either intrachromosomal or extrachromo-
somal DNA. See also 
IN VITRO SELECTION
.
Amplified Fragment Length Polymorphism
Also known by its acronym, AFLP is a
“DNA marker” utilized in a “genetic map-
ping” technique which employs the specific
sequence of bases (nucleotides) in a piece of
DNA (from an organism). Since the specific
sequence of bases in their DNA molecules
is different for each species, strain, variety,
or individual (due to DNA polymorphism),
AFLP can be used to “map” those DNA
molecules (e.g., to assist and speed up plant
breeding programs). See also 
GENETIC MAP
,
SEQUENCE
  (
OF A DNA MOLECULE
),
DEOXYRIBO-
NUCLEIC ACID
  (
DNA
),
GENOME
,
PHYSICAL MAP
(
OF GENOME
),
MARKER
  (
DNA SEQUENCE
),
© 2002 by CRC Press LLC

A
MARKER
  (
GENETIC MARKER
),
POLYMORPHISM
(
CHEMICAL
),
NUCLEIC ACIDS
,
NUCLEOTIDE
,
GENETIC CODE
.
Amplimer See
AMPLICON
.
Amylase A term that is used to refer to a cat-
egory of enzymes that catalyzes the chemi-
cal reaction in which amylose (starch)
molecules are hydrolytically cleaved (bro-
ken) to molecular pieces (e.g., the polysac-
charides maltose, maltotriose, a-dextrin,
etc.). For example, 
α-amylase is used to
break apart corn starch molecules in the first
step of manufacturing fructose (sweetener
for soft drinks). Since 1857, amylase has
been utilized to remove (amylose) starch
from woven fabrics in the textile industries.
Modern uses of some amylases include
enabling the substitution of barley grain for
malt in the beer brewing process. See also
ENZYME
,
STARCH
,
AMYLOSE
,
BARLEY
,
HYDRO-
LYTIC CLEAVAGE
,
POLYSACCHARIDES
,
ALPHA
AMYLASE INHIBITOR
-
1
.
Amyloid
␤ Protein Precursor (A␤PP)
A (collective) set of protein molecules, from
which are derived Amyloid 
β Protein (AβP).
See also 
PROTEIN
,
AMYLOID
β
PROTEIN PRECUR-
SOR
 (
A
β
PP
).
Amyloid
␤ Protein (A␤P) A small protein
that forms plaque in the brains and in the brain
blood vessels of victims of Alzheimer’s dis-
ease. A
βP forms cation-selective ion channels
in lipid bilayers (e.g., membranes surround-
ing cells). This ion channel formation disrupts
calcium homeostasis, allowing (destructive)
high concentrations of calcium ions in brain
cells. See also 
PROTEIN
,
AMYLOID
β
PROTEIN
PRECURSOR
 (
A
β
PP
),
ALZHEIMER
’
S DISEASE
.
Amyloid Placques See
AMYLOID
β
PROTEIN
 (
A
β
P
).
Amylopectin The form of starch (molecule)
that consists of multi-branched polymers,
containing approximately 100,000 glucose
units per molecule (polysaccharide). See
also
STARCH
,
POLYMER
,
GLUCOSE
  (
GL
c
),
POLYSACCHARIDES
,
WAXY CORN
.
Amylose The form of starch that consists of
unbranched polymers, containing approxi-
mately 4000 glucose units per molecule
(polysaccharide). It is present in potatoes at
23–29% content (variation is thought to be
caused by different growing conditions). See
also
POLYMER
,
GLUCOSE
  (
GL
c
),
AMYLASE
,
POLYSACCHARIDES
.
Anabolism The phase of intermediary metab-
olism concerned with the energy-requiring
biosynthesis of cell components from
smaller precursor molecules. See also
CATABOLISM
,
ASSIMILATION
,
METABOLISM
,
CELL
,
PLASMA MEMBRANE
.
Anaerobe An organism that lives in the
absence of oxygen and generally cannot
grow in the presence of oxygen. The cata-
bolic metabolism of anaerobic micro-
organisms reduces a variety of organic and
inorganic compounds in order to survive
(e.g., carbon dioxide, sulfate, nitrate, fuma-
rate, iron, manganese); anaerobes produce a
large number of end products of metabolism
(e.g., acetic acid, propionic acid, lactic acid,
ethanol, methane, etc.). See also 
CATABOLISM
,
METABOLISM
,
METABOLITE
,
REDUCTION
  (
IN A
CHEMICAL REACTION
),
ANAEROBIC
.
Anaerobic An environment without air or oxy-
gen. See also 
ANAEROBE
.
Analogue (Analog) A compound (or mole-
cule) that is a (chemical) structural derivative
of a parent compound. The word is also used
to describe a molecule that may be structur-
ally similar (but not identical) to another, and
which exhibits many or some of the same
biological functions of the other. For exam-
ple, the large class of antibiotics known as
the sulfa drugs are all analogues of the orig-
inal synthetic chemical drug (known as
Prontosil, which cures streptococcal infec-
tions) discovered by the German biologist
Gerhart Domagk. His discovery and others
made possible a program of further chemical
syntheses based upon the original (sulfanil-
amide) molecular structure and resulted in
the large number of sulfonamide (also called
“sulfa”) drugs available today. All of the ana-
logue (also analog) sulfa drugs that were
patterned after the original sulfanilamide
molecular structure may be called sulfanil-
amide analogues.
Today, analogues are known by man for
various vitamins, amino acids, purines, sug-
ars, growth factors, and many other chemical
compounds. Research chemists produce
analogues of various molecules in order to
ascertain the biological role of, or importance
© 2002 by CRC Press LLC

A
of, certain structures (within the molecule)
to the molecule’s function within a living
organism. See also 
BIOMIMETIC MATERIALS
,
RATIONAL DRUG DESIGN
,
HETEROLOGY
,
GIBBER-
ELLINS
,
QUANTITATIVE STRUCTURE
-
ACTIVITY
RELATIONSHIP
 (
QSAR
).
ANDA (to FDA) Abbreviated New Drug
Application (to the U.S. Food and Drug
Administration). See also 
NDA
, “
TREATMENT
”
IND REGULATIONS
,
FOOD AND DRUG ADMINISTRA-
TION
 (
FDA
).