Biotechnology

Spontaneous Assembly See
SELF
-
ASSEMBLY
.
SPS Acronym for the Sanitary and Phytosani-
tary Standards Agreement of the World
Trade Organization (WTO), a multinational
trading agreement that “sets the rules” gov-
erning international trade. Sanitary (i.e.,
human and animal) and phytosanitary (i.e.,
plant) standards are important in preventing
the transfer of diseases from one nation to
another via international trade. SPS stan-
dards are designed to protect animal, plant,
and human life/health (within WTO member
countries) from:
• Entry of pests (insects, weeds, etc.)
• Entry of disease-carrying organisms
(e.g., European Corn Borer)
• Entry of disease-causing organisms
(e.g., Aspergillus flavus)
• Toxins, contaminants, or disease-caus-
ing organisms in foods, beverages, or
feedstuffs
© 2002 by CRC Press LLC

S
WTO member nations are required to base
their SPS standards as much as possible on
existing (e.g., Codex Alimentarius, IPPC,
and OIE) international sanitary/phytosani-
tary standards and practices. See also 
SANI-
TARY AND PHYTOSANITARY
  (
SPS
)
AGREEMENT
,
SANITARY AND PHYTOSANITARY
  (
SPS
)
AGREE-
MENT
,
INTERNATIONAL PLANT PROTECTION CON-
VENTION
  (
IPPC
),
INTERNATIONAL OFFICE OF
EPIZOOTICS
 (
OIE
),
CODEX ALIMENTARIUS COMMIS-
SION
,
MAXIMUM RESIDUE LEVEL
  (
MRL
),
WORLD
TRADE ORGANIZATION
  (
WTO
),
EUROPEAN CORN
BORER
 (
ECB
),
ASPERGILLUS FLAVUS
.
Squalamine A potent antimicrobial agent (ste-
roid, antibiotic) discovered in the tissues of
the dogfish shark in 1992. It has been found
to be active against a broad spectrum of bac-
teria, protozoa, and fungi. Squalamine was
chemically synthesized by man in 1993. See
also
MAGAININS
,
STEROID
,
FUNGUS
,
BACTERIA
,
BACTERIOCINS
,
PROTOZOA
,
ANTIBIOTIC
.
Squalene A sterol that is produced in some
plants. See also 
STEROLS
.
SRB (sulfate reducing bacterium) Any organ-
ism that metabolically reduces sulfate to H
2
S
(hydrogen sulfide). This includes a variety
of microorganisms. See also 
REDUCTION
 (
IN A
CHEMICAL REACTION
),
METABOLISM
,
MICROOR-
GANISM
,
FERROBACTERIA
.
SSR See
SIMPLE SEQUENCE REPEAT
  (
SSR
)
DNA
MARKER TECHNIQUE
.
Stacchyose See
STACHYOSE
.
Stachyose A carbohydrate (oligosaccharide)
naturally produced in soybeans (and some
other plants). Stachyose is relatively insolu-
ble in water, and much less available for
digestion by monogastric animals (e.g.,
swine, poultry) than the other carbohydrate
components within soybeans. See also 
CAR-
BOHYDRATES
  (
SACCHARIDES
),
LOW STACHYOSE
SOYBEANS
,
OLIGOSACCHARIDES
,
SOYBEAN PLANT
.
“Stacked” Genes Refers to the insertion of
two or more (synthetic) genes into the
genome of an organism. One example would
be of a plant into which a gene from Bacillus
thuringiensis (B.t.) and a gene for resistance
to a specific herbicide have been inserted.
See also 
GENE
,
BIOTECHNOLOGY
,
GENETIC ENGI-
NEERING
,
BACILLUS THURINGIENSIS
  (
B
.
t
.),
B
.
t
.
KURSTAKI
,
GENETICALLY ENGINEERED MICROBIAL
PESTICIDES
  (
GEMP
),
EPSP SYNTHASE
,
PAT GENE
,
BAR GENE
.
Staggered Cuts Scissions (cuts) made in
duplex DNA when the two strands of DNA
that make up the duplex DNA are cleaved at
different points near each other by restriction
endonucleases. What is produced is a single-
stranded structure (in which the single strands
are a number of nucleotide bases long) with
a double-stranded core section. This core sec-
tion is much longer than the single-stranded
region. See also 
DEOXYRIBONUCLEIC ACID
 (
DNA
),
RESTRICTION ENDONUCLEASES
,
STICKY ENDS
.
Stanol Ester See
SITOSTANOL
.
Stanol Fatty Acid Esters S e e
S I T O S T A N O L
,
FATTY ACID
.
Starch A polymer of glucose molecules (i.e.,
a polysaccharide) used by plants to store
energy. Plants produce starch in two differ-
ent molecular forms, amylopectin and amy-
lose. For example, the starch content in
traditional corn (maize) kernels averages
72–76% amylopectin and 24–28% amylose.
Starch is broken down by enzymes (amy-
lases) to yield glucose, which can be used
as an energy source. The analogous polymer
used by mammalian systems is called gly-
cogen or, in old usage, “animal starch.” See
also
GLUCOSE
 (
GL
c
),
ENZYME
,
AMYLASE
,
CORN
,
AMYLOSE
,
AMYLOPECTIN
.
Startpoint Refers to the position on a DNA
molecule corresponding to the first base
incorporated into mRNA. See also 
DEOXY-
RIBONUCLEIC ACID
  (
DNA
),
MESSENGER RNA
(
m
RNA
),
EXON
,
RIBONUCLEIC ACID
 (
RNA
).
Stearate (stearic acid) A saturated fatty acid,
containing 18 carbon atoms in its molecular
“backbone,” that is essentially neutral in
effect on coronary heart disease in humans
(i.e., doesn’t appreciably increase low-den-
sity lipoproteins in the bloodstream). Because
of the heart disease neutrality, stearate-con-
taining oils (e.g., high-stearate soybean oil)
are an acceptable cooking oil choice, with
the resistance to oxidation/breakdown of a
saturated fatty acid, but no bloodstream-cho-
lesterol increasing effect.
In the mid-1990s, the American Cocoa
Research Institute/Chocolate Manufacturers
Association filed a petition with the U.S.
Food and Drug Administration (FDA) to
© 2002 by CRC Press LLC

S
differentiate stearate (on food product labels)
from the other saturated long-chain fatty acids
used as food ingredients.
In order to make milk, dairy cows require
more stearic acid than a conventional diges-
tive system alone could provide from the
cow’s (mainly carbohydrate) diet. Therefore,
cows utilize microorganisms living in their
rumen (a special sort of pre-stomach) to con-
vert carbohydrate (grass) to stearic acid.
Thus, high-performance dairy cows might
benefit from a diet that contains high-stear-
ate soybeans, if their milk output is limited
by dietary stearate availability. See also
FATTY ACID
,
LOW
-
DENSITY LIPOPROTEINS
 (
LDLP
),
SATURATED FATTY ACIDS
,
FOOD AND DRUG
ADMINISTRATION
  (
FDA
),
HIGH
-
STEARATE SOY-
BEANS
,
FATS
,
ENOYL
-
ACYL PROTEIN REDUCTASE
,
HIGH
-
STEARATE CANOLA
.
Stearic Acid See
STEARATE
.
Stearoyl-ACP Desaturase A “ f a m i l y ”   o f
enzymes that is naturally produced in oilseed
plants. They play the central role in deter-
mining the ratio of saturated to unsaturated
fatty acids (in the vegetable oils produced
from such plants). See also 
FATS
,
FATTY ACID
,
ENZYME
,
GENETIC ENGINEERING
,
GENETIC CODE
,
LAURATE
,
HIGH
-
STEARATE SOYBEANS
,
HIGH
-
STEARATE CANOLA
.
Stem Cell Growth Factor (SCF) A growth
factor (glycoprotein hormone) that acts upon
stem cells in a wide variety of ways to
increase growth, proliferation, and maturity
(into red blood cells or white blood cells).
See also 
STEM CELLS
,
GROWTH FACTOR
,
HOR-
MONE
,
GLYCOPROTEIN
,
DIFFERENTIATION
,
TOTI-
POTENT STEM CELLS
,
COLONY STIMULATING
FACTORS
 (
CSF
s
).
Stem Cell One The single stem cell in the
bone marrow of a fetus from which every
immune system cell in the adult is subse-
quently derived. The primordial stem cell is
stimulated to develop into the mature
immune system’s differentiated, specialized
cells by interleukin-7. See also 
STEM CELLS
,
TOTIPOTENT STEM CELLS
,
INTERLEUKIN-
7
  (
IL-
7
),
EMBRYONIC STEM CELLS
,
DIFFERENTIATION
.
Stem Cells Certain cells — present in the bod-
ies of mammals even prior to birth, although
also present in adult mammals — that can
grow/differentiate into different cells/tissues
of the (adult organism) body. For example,
bone marrow (stem) cells, some of which
eventually mature into red blood cells or
white blood cells. The stem cells that remain
in the bone marrow maintain their own num-
bers by self-renewal divisions, yielding more
cells to start the maturation process. This
maturation process is stimulated and con-
trolled by stem cell growth factor (SCF),
granulocyte colony stimulating factor
(G-CSF), and by granulocyte-macrophage
colony stimulating factor (GM-CSF).
During 2000, research by Richard Childs
showed that stem cells (i.e., collected from
a sibling’s bloodsteam) transplanted into a
patient suffering from kidney cancer could
induce generation of a “new” immune sys-
tem which could help stop/reverse the kid-
ney cancer. See also 
CELL
,
MULTIPOTENT ADULT
STEM CELLS
,
ECTODERMAL ADULT STEM CELLS
,
ENDODERMAL ADULT STEM CELLS
,
MESODERMAL
ADULT STEM CELLS
,
HEMATOPOIETIC STEM CELLS
,
RED BLOOD CELLS
,
WHITE BLOOD CELLS
,
BASO-
PHILS
,
STEM CELL ONE
,
STEM CELL GROWTH FACTOR
(
SCF
),
TOTIPOTENT STEM CELLS
,
TOTIPOTENCY
,
EMBRYONIC STEM CELLS
,
DIFFERENTIATION
,
IMMUNE RESPONSE
,
CANCER
.
Stereoisomers Molecules that have the same
structural formula but different spatial
arrangements of dissimilar groups (of
atoms) bonded to a common atom (in the
molecule). Many of the physical and chem-
ical properties of stereoisomers are the same,
but there are differences in the crystal struc-
tures, in the direction in which they rotate
polarized light (which has been passed
through a solution of the stereoisomer), and
in their use in an enzyme-catalyzed (biolog-
ical) reaction. See also 
RACEMATE
,
POLARIME-
TER
,
DEXTROROTARY
  (
D
)
ISOMER
,
EPIMERS
,
ISOMER
,
LEVOROTARY
  (
L
)
ISOMER
,
ISOMERASE
,
DIASTEREOISOMERS
.
Steric Hindrance Refers to the compression
that a group (chemical entity) suffers by
being too close to its nonbonded neighbors.
If an enzyme and a substrate try to come
together in order to react, but the substrate
has on it a bulky group that disallows close
contact between the two (because the group
bumps into the enzyme), then the reaction
will not occur because of steric hindrance.
© 2002 by CRC Press LLC

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Seen another way, two chemical groups
bump into each other and cannot get by each
other because they are held in place by the
bonds binding them to other atoms. Hin-
drance of movement or activity occurs
because chemical groups bump into each
other and cannot occupy the same space. See
also
REPRESSION
  (
OF AN ENZYME
),
INHIBITION
,
COREPRESSOR
.
Sterile (environment) One that is free of any
living organisms or spores. For example, a
hypodermic needle that has been sterilized
(e.g., by heating it) and is free of living
microorganisms is said to be sterile.
Sterile (organism) One that is unable to repro-
duce. For example, a bull that has been cas-
trated is rendered sterile. See also 
TRIPLOID
,
BARNASE
.
Sterilization See
STERILE
 (
ENVIRONMENT
),
STER-
ILE
 (
ORGANISM
).
Steroid A chemical compound composed of a
series of four carbon rings joined together to
form a (molecular) structural unit called cyclo-
pentanoperhydrophenanthrene. Any of a group
of naturally occurring, fat-soluble substances
essential to life, usually classed as lipids.
Steroids of importance to the body are the
sterols, which are bile acids (produced by
the liver, characterized by the presence of a
carboxyl group in the molecule’s side chain),
and the hormones of the sex glands and the
adrenal cortex. In addition, the plant king-
dom possesses a wide variety of steroid gly-
cosides. See also 
GLYCOSIDE
,
LIPIDS
,
HORMONE
,
CHOLESTEROL
,
STEROLS
,
SAPONINS
.
Sterols Solid alcohols consisting of ring-struc-
tured molecules (i.e., a ‘ring’ made of
atoms). Evidence suggests that human con-
sumption of certain phytosterols (i.e., sterols
produced in plant seeds) can help to prevent
certain types of cancers, and can help lower
levels of total blood serum cholesterol and
low-density lipoproteins (LDLP); thereby
reducing risk of coronary heart disease
(CHD). Evidence indicates that those phy-
tosterols interfere with absorption of choles-
terol by the intestines, and they decrease the
body’s recovery and reuse of cholesterol-
containing bile salts, which causes more
cholesterol to be excreted from the body.
During 2000, researcher Joseph Judd fed
phytosterols extracted from soybeans (Gly-
cine max L.) to human volunteers who were
already consuming a “low fat” diet. Their
total blood serum cholesterol and low-den-
sity lipoprotein (LDLP) levels decreased by
more than 10%, in a short time. During 2001,
the U.S. FDA approved a (label) health claim
that associates the consumption of plant ste-
rols with reduced blood cholesterol content,
and with reduced coronary heart disease
(CHD). Some of the sterols known to impart
health benefits when consumed by humans
include
β-sitosterol (beta-sitosterol) and
squalene. See also 
PHYTOSTEROLS
,
STEROID
,
CHOLESTEROL
,
BILE
,
SITOSTANOL
,
SOYBEAN PLANT
,
CAMPESTEROL
,
STIGMASTEROL
,
BETA
-
SITOSTEROL
,
CORONARY HEART DISEASE
 (
CHD
),
LOW
-
DENSITY
LIPOPROTEINS
 (
LDLP
),
FOOD AND DRUG ADMINIS-
TRATION
 (
FDA
).
Sticky Ends Complementary single strands of
DNA (deoxyribonucleic acid) that protrude
from opposite ends of a DNA duplex or from
ends of different DNA duplex molecules.
They can be generated by staggered cuts in
DNA. They are called “sticky” because the
exposed single strands can bind (stick) to
complementary single strands on another
DNA molecule. A hybrid piece of DNA is
hence produced (by that binding). See also
STAGGERED CUTS
,
HYBRIDIZATION
  (
MOLECULAR
GENETICS
),
DUPLEX
,
ANNEAL
,
DEOXYRIBONUCLEIC
ACID
 (
DNA
),
BLUNT
-
END LIGATION
,
RESTRICTION
ENDONUCLEASES
.
Stigmasterol A phytosterol produced within
the seeds of the soybean plant (Glycine
max L.), among others. Evidence indicates
that human consumption of stigmasterol
helps reduce levels of total serum cholesterol
and low-density lipoproteins (LDLP); thereby
lowering risk of coronary heart disease
(CHD). Evidence indicates that certain phy-
tosterols (including stigmasterol) interfere
with absorption of cholesterol by the intes-
tines, and decrease the body’s recovery and
reuse of cholesterol-containing bile salts;
which causes more cholesterol to be excreted
from the body. See also 
PHYTOSTEROLS
,
PHYTO-
CHEMICALS
,
STEROLS
,
SOYBEAN PLANT
,
CHOLES-
T E R O L
,
C A M P E S T E R O L
,
B E T A
-
S I T O S T E R O L
,
CORONARY HEART DISEASE
 (
CHD
).
© 2002 by CRC Press LLC

S
Stomatal Pores See
GPA
1
,
ABSCISIC ACID
.
Strain A group or organisms of the same spe-
cies that possess(es) distinctive genetic char-
acteristics that set it apart from others within
the same species, but whose differences are
not “severe” enough for it to be considered
a different breed or variety (of that species).
The basic taxonomic unit of microbiology.
Can also be used to designate a population
of cells derived from a single cell. See also
SPECIES
,
CELL
,
CLONE
 (
AN ORGANISM
).
Streptococcus Refers to bacteria of the genus
Streptococcus. See also 
BACTERIA
,
GENUS
,
STREPTOCOCCUS MUTANS
.
Streptococcus mutans The strain of Strepto-
coccus bacteria that grows on the surface of
teeth and can contribute to causing tooth
“decay.” See also 
STRAIN
,
BACTERIA
,
STREPTO-
COCCUS
.
Stress Proteins Discovered by Italian biolo-
gist Ferruchio Ritossa in the 1960s, these
molecules are also called heat-shock pro-
teins. Proteins made by many organisms’
(plant, bacteria, and mammal) cells when
those cells are stressed by environmental
conditions such as certain chemicals, patho-
gens, or heat.
When corn/maize (Zea mays L.)  is
stressed during its growing season by high
nighttime temperatures, that plant switches
from its normal production of (“immune sys-
tem” defense) chitinase to production of
heat-shock (i.e., stress) proteins, instead.
Stress proteins are also produced by
tuberculosis and leprosy bacteria after these
bacteria have invaded (infected) cells in the
human body, in an attempt by those bacteria
to mimic the stress proteins that (mammal)
cells would normally manufacture to repair
damage done to the (mammal) cells. This
mimicry makes it more difficult for the
immune system to recognize and attack
those pathogenic bacteria (and/or repair mis-
shaped protein molecules in the body’s
cells). Similarly, production of stress pro-
teins helps some types of cancer cells to
avoid being attacked by the immune system.
Because consumption of genistein by
humans causes a reduction in the production
of stress proteins, genistein may thereby
help the human immune system destroy
cancerous cells. In 1996, Richard I. Morim-
oto discovered that two stress proteins
known as HSP 90 and HSP 70 help ensure
that certain crucial proteins in cells are
folded into the configuration/conformation
needed by that cell. See also 
ANTIGEN
,
IMMUNE
RESPONSE
,
PATHOGEN
,
PROTEIN
,
PROTEIN FOLD-
ING
,
CONFORMATION
,
CHAPERONES
,
PROTEIN
STRUCTURE
,
ABSOLUTE CONFIGURATION
,
PRION
,
CHITINASE
,
AFLATOXIN
,
GENISTEIN
,
CANCER
,
LIPOXYGENASE
 (
LOX
),
PHYTOALEXINS
.
Stromelysin (MMP-3) A collagenase (enzyme)
that “clears a path” through living tissue,
ahead of tumor cells, thereby enabling a can-
cer to spread within the body. See also
COLLAGENASE
,
ENZYME
,
CANCER
,
TUMOR
.
Structural Biology See
STRUCTURAL GENE
.
Structural Gene A gene that codes for any
RNA (ribonucleic acid) or protein product
other than a regulator molecule. It deter-
mines the primary sequences (i.e., the amino
acid sequences) of a polypeptide (protein).
See also 
GENE
,
EXPRESS
,
POLYPEPTIDE
 (
PROTEIN
),
AMINO ACID
,
PRIMARY STRUCTURE
,
RIBONUCLEIC
ACID
 (
RNA
).
Structural Genomics Study of, or discovery
of, where (gene) sequences are located
within the genome, and what (DNA) sub-
units comprise those sequences. See also
GENE
,
SEQUENCE
 (
OF A DNA MOLECULE
),
DEOXY-
RIBONUCLEIC ACID
 (
DNA
),
SEQUENCING
 (
OF DNA
MOLECULES
),
GENOME
,
GENOMICS
,
PRIMARY
STRUCTURE
.
STS Sulfonylurea (Herbicide)-Tolerant Soy-
beans These are soybeans that have been
bred (via insertion of ALS gene by tradi-
tional breeding methods) to resist the (weed
killing) effects of sulfonylurea-based herbi-
cides. The ALS gene was discovered by
Scott Sebastian in 1986. See also 
GENE
,
GENETIC ENGINEERING
,
HTC
,
ALS
,
ALS GENE
,
BAR
GENE
,
PAT GENE
,
EPSP SYNTHASE
,
GLYPHOSATE
OXIDASE
,
HERBICIDE
-
TOLERANT CROP
.
Stx Shiga-like toxins. See also 
TOXIN
,
TOXI-
GENIC E
.
COLI
,
ENTEROHEMORRHAGIC E
.
COLI
,
ESCHERICHIA COLIFORM
0157
:
H
7
 (
E
.
COLI
0157
:
H
7
).
Substance K See
TACHYKININS
.
Substance P A neuropeptide (i.e., peptide pro-
duced by cells of the nervous system) which
is involved in activation of the immune sys-
tem, pain sensation, and (when in excess)
© 2002 by CRC Press LLC