Biotechnology

Site-Directed Mutagenesis (SDM) A   t e c h -
nique that can be used to make a protein that
differs slightly in its structure from the pro-
tein normally produced (by an organism or
cell). A single mutation (in the cell’s DNA)
is caused by hybridizing the region in a
codon to be mutated with a short, synthetic
oligonucleotide. This causes the codon to
code for a different specific amino acid in
the protein gene product. Site-directed
mutagenesis holds the potential to enable
man to create modified (engineered) proteins
that have desirable properties not currently
available in the proteins produced by exist-
ing organisms. See also 
MUTANT
,
MUTATION
,
POINT MUTATION
,
PROTEIN
,
GENE
,
INFORMA-
TIONAL MOLECULES
,
HEREDITY
,
GENETIC CODE
,
GENETIC MAP
,
AMINO ACID
,
DEOXYRIBONUCLEIC
ACID
 (
DNA
),
CODON
,
OLIGONUCLEOTIDE
,
PROTEIN
ENGINEERING
.
Sitostanol A chemical (ester) derived from
sitosterol (a sterol present in pine trees), and
fibers (e.g., the hull or seed coat) of
corn/maize (Zea mays) or soybeans (Glycine
max L.). When sitostanol is consumed by
humans in sufficient quantities, it causes
their total serum cholesterol and their low-
density lipoprotein (LDLP) levels to be low-
ered by approximately 10%, via inhibition
(i.e., the sitostanol is preferentially absorbed
by the gastrointestinal system instead of cho-
lesterol). During 2000, the U.S. Food and
Drug Administration approved a (label)
health claim that associates consumption of
© 2002 by CRC Press LLC

S
sitostanols with reduced blood cholesterol
content and with reduced coronary heart dis-
ease (CHD). See also 
ABSORPTION
,
DIGESTION
(
WITHIN ORGANISMS
),
SOYBEAN PLANT
,
LOW
-
DENSITY LIPOPROTEINS
 (
LDLP
),
SERUM LIFETIME
,
CHOLESTEROL
,
STEROLS
,
PHYTOSTEROLS
,
SITO-
STEROL
,
CORONARY HEART DISEASE
 (
CHD
).
Sitosterol A phytosterol that is naturally pro-
duced in fibers within soybean (Glycine
max L.) hulls, pumpkin seeds, pine trees,
fibers of corn/maize (Zea mays) seed coats,
etc. Sitosterol can exist in several different
molecular forms (known as alpha a, beta b,
etc.). A human diet containing large amounts
of sitosterol and/or certain other phytosterols
(campesterol, stigmasterol, etc.) has been
shown to lower total serum (blood) choles-
terol and low-density lipoprotein (LDLP)
levels; and thereby lower the risk of coronary
heart disease (CHD).
Evidence indicates that certain phytoster-
ols (including sitosterol) interfere with
absorption of cholesterol by the intestines,
and decrease the body’s recovery and reuse
of cholesterol-containing bile salts, which
causes more cholesterol to be excreted from
the body than previously. During 2000, the
U.S. Food and Drug Administration
approved a (label) health claim that associ-
ates consumption of sitosterols with reduced
blood cholesterol content and with reduced
coronary heart disease (CHD). See also 
PHY-
TOSTEROLS
,
SOYBEAN PLANT
,
CORN
,
STEROLS
,
SITOSTANOL
,
CAMPESTEROL
,
STIGMASTEROL
,
COR-
ONARY HEART DISEASE
 (
CHD
),
BETA
-
SITOSTEROL
,
CHOLESTEROL
.
SK See
SUBSTANCE K
.
Slime An extracellular (i.e., outside of the cell)
material produced by some (micro)organ-
isms and characterized by a slimy consis-
tency. The slime is of varied chemical
composition. However, usual components
are polysaccharides (polysugars) and specific
protein molecules.
Smut See
TELETHIA CONTROVERSIA KOON SMUT
.
SNP See
SINGLE
-
NUCLEOTIDE POLYMORPHISMS
(
SNP
s
).
SNP MAP A group of known/detailed SNPs
(single-nucleotide polymorphisms), super-
imposed onto the genome map of an organism
(e.g., to facilitate genetic/population studies,
such as of genetically related disease suscep-
tibility). See also 
SINGLE
-
NUCLEOTIDE POLY-
M O R P H I S M S
  (
S N P
s
),
O R G A N I S M
,
G E N O M E
,
GENOMIC SCIENCES
,
MAPPING
 (
OF GENOME
),
MAP
DISTANCE
,
MARKER
 (
DNA SEQUENCE
).
SNP MARKERS S e e
S I N G L E
-
N U C L E O T I D E
POLYMORPHISMS
 (
SNP
s
).
Sodium Dodecyl Sulfate See
SDS
.
Sodium Lauryl Sulfate See
SDS
.
Solanine A glycoside neurotoxin naturally
present at low levels within potatoes. As a
result, solanine is present at detectable levels
in the bloodstream of humans who consume
potatoes. The U.S. Food and Drug Admin-
istration (FDA) prohibits the sale in the U.S.
of potatoes which contain more (than a very
low level of solanine); e.g., the naturally
present level in potatoes can unfortunately
increase in potatoes that are exposed to
direct sunlight. See also
TOXIN
,
PHYTOTOXIN
,
CHACONINE
,
GLYCOSIDE
,
WILD TYPE
,
FOOD AND
DRUG ADMINISTRATION
  (
FDA
),
TRADITIONAL
BREEDING METHODS
.
Solid-Phase Synthesis See
SYNTHESIZING
  (
OF
PROTEINS
),
SYNTHESIZING
 (
OF DNA MOLECULES
).
Soluble CD4 A synthetic version of the CD4
protein that may interfere with the ability of
HIV (i.e., AIDS) viruses to infect human
immune system cells with the acquired
immune deficiency syndrome (AIDS) virus.
See also 
CD
4
PROTEIN
,
ADHESION MOLECULE
,
SELECTINS
,
LECTINS
,
PROTEIN
.
Soluble Fiber See
WATER SOLUBLE FIBER
.
Somaclonal Variation The genetic variation
(i.e., new traits) that results from the growing
of entire new plants from plant cells or tis-
sues (e.g., maintained in culture). Frequently
encountered when plants are regenerated
(grown) from plant cells that have been
altered via genetic engineering. However,
somaclonal variation (i.e., new genetic traits)
can occur even when plants are regenerated
from cells that were part of the same original
plant. See also 
CELL CULTURE
,
SOMATIC VARI-
ANTS
,
CLONE
  (
AN ORGANISM
),
AGROBACTERIUM
TUMEFACIENS
,
BIOLISTIC
®
GENE GUN
, “
EXPLOSION
”
METHOD
,
SHOTGUN METHOD
.
Somatacrin See also 
G R O W T H
H O R M O N E
-
RELEASING FACTOR
 (
GRF
or
GHRF
).
© 2002 by CRC Press LLC

S
Somatic Cells All eucaryote body cells except
the gametes and the cells from which they
develop. See also 
GAMETE
,
OOCYTES
.
Somatic Variants Regenerated plants (i.e.,
clones) derived (produced) from cells that
originally came from the same plant, but are
not genetically identical. Such plants
(clones) are called “sports” or somatic vari-
ants because they vary (genetically) from the
“parent” plant. Sometimes such somatic
variants are developed by man to become a
new plant variety (e.g., the nectarine is an
example of this). See also 
SOMACLONAL VARI-
ATION
,
CELL CULTURE
,
CLONE
  (
AN ORGANISM
),
GENOTYPE
.
Somatomedins A family of peptides that
mediates the action of growth hormone on
skeletal tissue, and stimulates bone forma-
tion. See also 
HUMAN GROWTH HORMONE
 (
HGH
),
PEPTIDE
,
BONE MORPHOGENETIC PROTEINS
 (
BMP
).
Somatostatin A 14 amino acid peptide that
inhibits the release of growth hormone. See
also
HUMAN GROWTH HORMONE
 (
HGH
),
GROWTH
HORMONE
-
RELEASING FACTOR
  (
GRF
or
GHRF
),
PEPTIDE
.
Somatotropin Category of hormone that is
produced naturally in the bodies of all mam-
mals, including man. See also 
HORMONE
,
GROWTH HORMONE
,
BOVINE SOMATOTROPIN
 (
BST
),
PORCINE SOMATOTROPIN
 (
PST
).
SOS Protein See
SOS RESPONSE
 (
IN ESCHERICHIA
COLI BACTERIA
).
SOS Response (in Escherichia coli bacteria)
The “switching on” of genetic repair
machinery in this bacteria when its DNA has
been damaged (e.g., by radiation). See also
ESCHERICHIA COLIFORM
 (
E
.
COLI
).
Southern Blot Analysis A test that is per-
formed on biological samples such as plant
DNA (e.g., to ascertain if “inserted” DNA is
present in particular plant cells). Gel elec-
trophoresis is used to separate the DNA frag-
ments according to size, and then those
fragments are transferred to a filter (blot).
Radiolabeled DNA probes or RNA probes
are added, and the ones which are comple-
mentary to each of the (separated, on blot)
fragments will hybridize to those respective
DNA fragments. The location (on the blot)
and “radioactive label” of those hybridized
probes can then be utilized to determine the
nature of the DNA that was in those plant
cells. See also 
DEOXYRIBONUCLEIC ACID
 (
DNA
),
RIBONUCLEIC ACID
 (
RNA
),
GENETIC ENGINEERING
,
ELECTROPHORESIS
,
TWO
-
DIMENSIONAL
  (
2
D
)
GEL
ELECTROPHORESIS
,
POLYACRYAMIDE GEL ELEC-
TROPHORESIS
  (
PAGE
),
RADIOLABELED
,
DNA
PROBE
,
COMPLEMENTARY
  (
MOLECULAR GENET-
ICS
),
HYBRIDIZATION
  (
MOLECULAR GENETICS
),
RADIOIMMUNOASSAY
.
Southern Corn Rootworm Latin name
Diabrotica undecimpunctata hawardii. See
also
CORN ROOTWORM
.
Soy Protein An edible protein (after heat pro-
cessing) produced within its beans (seeds)
by the soybean plant (botanical name Gly-
cine max (L.) Merrill). When removed from
soybeans via crushing, extrusion, or other
process(es) involving adequate heat treat-
ment, soy protein is (historical average)
composed of 2.5% cysteine, 3.4% histidine,
5.2% isoleucine, 8.2% leucine, 6.8% lysine,
1.1% methionine, 5.6% phenylalanine, 4.2%
threonine, 1.3% tryptophan, 4.2% tyrosine,
5.4% valine, 4% alanine, 7.7% arginine, 6.9%
aspartic acid, 19% glutamic acid, 3.7% gly-
cine, 0.1% 4-hydroxyproline, 5.3% proline,
and 5.4% serine. Soy protein (concentrate) is
a complete (“ideal”) protein (i.e., it provides
all essential amino acids) for humans. It is a
good dietary source of calcium, with an
absorption rate equivalent to milk.
In its initial form (i.e., following crush-
ing/extrusion from soybeans as described
above), the soy protein is known as soybean
meal, and contains a bit less than half protein
by weight. If the soy is washed with water
(following crushing/extrusion) to remove
soluble polysaccharides (e.g., the carbohy-
drates known as stachyose, raffinose, etc.),
the resultant soy protein is known as soy
protein concentrate and contains approxi-
mately 60% protein by weight. If the soy is
washed with water-and-alkali solution, fol-
lowed by isoelectric precipitation of the sol-
uble protein, the result is “isolated soy
protein” (ISP), often known as soy protein
isolate or soy isolate. In 1999, the U.S. FDA
approved a (label) health claim that associ-
ates consumption of soy protein with
reduced blood cholesterol content and with
reduced coronary heart disease (CHD) in
© 2002 by CRC Press LLC

S
humans. See also 
SOYBEAN PLANT
,
TRYPSIN
INHIBITORS
,
PROTEIN
,
CHOLESTEROL
,
CORONARY
HEART DISEASE
  (
CHD
),
AMINO ACID
,
ESSENTIAL
AMINO ACIDS
, “
IDEAL PROTEIN
”
CONCEPT
,
PROTEIN
DIGESTIBILITY
-
CORRECTED AMINO ACID SCORING
(
PDCAAS
),
STACHYOSE
.
Soybean Aphid An aphid (Aphis glycines)
native to China, but accidentally introduced
into the U.S. during the 1990s (apparently
via aphid eggs adhering to an ornamental
plant). It feeds on the sap of the soybean
plant (Glycine max L.). See also 
SOYBEAN
PLANT
.
Soybean Cyst Nematodes (SCN) Microscopic
roundworms (Heterodera glycines) living in
the soil, which feed parasitically on roots of
the soybean plant. The nematodes use a
spear-like mouthpart, called a stylet, to punc-
ture the plant’s root cells so the nematodes
can eat their cell contents. That root damage
causes the soybean’s growth to be stunted,
and the plants turn yellow because of a
reduction in nodule formation by the nitro-
gen-fixing Rhizobium bacteria (which nor-
mally colonize roots of soybean plants).
SCN can combine with a fungus (Fusarium
solani) to cause a soybean plant disease
known as “sudden death syndrome.”
As part of Integrated Pest Management
(IPM), farmers can utilize naturally resistant
soybean varieties (e.g., CystX) and/or the
parasitic Pasteuria bacteria to help control
the soybean cyst nematodes. The Pasteuria
bacteria must attach their spores (for repro-
duction) to juvenile nematodes, so that the
Pasteuria offspring can consume the SCN
when the spores later germinate. See also
SOYBEAN PLANT
,
NITROGEN FIXATION
,
BACTERIA
,
RHIZOBIUM
 (
BACTERIA
),
FUNGUS
,
SUDDEN DEATH
SYNDROME
,
ALLELOPATHY
,
ISOFLAVONES
,
NEMA-
TODES
,
CystX
.
Soybean Meal See
SOYBEAN PLANT
,
SOY PROTEIN
.
Soybean Oil An edible oil that is produced
within its beans (seeds) by the soybean plant
(botanical name Glycine max (L.)  Merrill).
When removed from soybeans via crushing
and refining processes, soybean oil is (his-
torical average) composed of 60.8% polyun-
saturated fatty acids (PUFA), 24.5%
monounsaturated fatty acids, and 15.1%
saturated fatty acids. However, soybean vari-
eties have recently been created that possess
as little as 7% saturated fatty acids. See also
POLYUNSATURATED FATTY ACIDS
  (
PUFA
),
FATTY
ACID
,
ESSENTIAL FATTY ACIDS
,
LECITHIN
,
HYDRO-
GENATION
,
SOYBEAN PLANT
,
HIGH
-
OLEIC OIL SOY-
B E A N S
,
L O W
-
L I N O L E N I C
O I L
S O Y B E A N S
,
LINOLENIC ACID
,
OLEIC ACID
,
LINOLEIC ACID
,
MONOUNSATURATED FATTY ACIDS
,
SATURATED
FATTY ACIDS
,
CONJUGATED LINOLEIC ACID
.
Soybean Plant B o t a n i c a l   n a m e   G l y c i n e
max (L.) Merrill. A green, bushy legume that
is the world’s single largest provider of pro-
tein and edible oil for mankind’s use. This
summer annual plant varies in height from
less than a foot (0.3 meter) to more than three
feet (one meter) tall. The seeds (soybeans)
are borne in pods, and historically have con-
tained 13–26% oil and 38–45% protein (on
a moisture-free basis). Its leaves contain
some carotenoids. The soybean plant has
approximately 80,000 genes. It is a self-pol-
linating plant (i.e., there are male and female
reproductive structures on the same plant —
so it is monoecious). Soybean oil contains a
total of 327 mg/100 g of the plant sterols
(phytosterols) campesterol, stigmasterol, and
beta-sitosterol (
β-sitosterol). Soybeans con-
tain the highest amount of isoflavones of any
plant (seeds) i.e., up to 0.3% of each soy-
bean’s dry weight. The traditional soybean,
possessing (average) 20% oil content, con-
tains an average of 3% stachyose within its
meal (i.e., the solids remaining after the soy-
bean oil is removed). See also 
FATTY ACID
,
PROTEIN
,
SOY PROTEIN
,
LECITHIN
,
NITROGEN FIX-
ATION
,
NODULATION
,
SOYBEAN OIL
,
SOYBEAN
CYST NEMATODES
  (
SCN
),
RESVERATROL
,
BROWN
STEM ROT
,
PHYTOPHTHORA ROOT ROT
,
PEROXI-
DASE
,
ISOFLAVONES
,
LOW
-
STACHYOSE SOYBEANS
,
GENISTEIN
 (
Gen
),
LIPOXYGENASE
 (
LOX
),
SAPONINS
,
CANOLA
,
CHLOROPLAST TRANSIT PEPTIDE
  (
CTP
),
HERBICIDE
-
TOLERANT CROP
,
LOX NULL
,
PHY-
TOSTEROLS
,
PHYTOCHEMICALS
,
CORN ROOTWORM
,
NITRIC OXIDE
 (
NO
),
MONOECIOUS
,
ALLELOPATHY
,
LOW
-
LINOLENIC OIL SOYBEANS
,
HIGH
-
OLEIC OIL
SOYBEANS
,
HIGH
-
PHYTASE
  (
SOYBEANS
),
HIGH
-
ISOFLAVONE SOYBEANS
,
HIGH
-
STEARATE SOY-
BEANS
,
HIGH
-
SUCROSE SOYBEANS
,
WATER SOLU-
B L E
F I B E R
,
L O W
-
P H Y T A T E
S O Y B E A N S
,
PHYTOPHTHORA MEGASPERMA
f. sp. 
GLYCINEA
,
STACHYOSE
,
PHYTOSTEROLS
,
CAMPESTEROL
,
© 2002 by CRC Press LLC

S
STIGMASTEROL
,
SITOSTEROL
,
BETA
-
SITOSTEROL
(
β
-
SITOSTEROL
),
SITOSTANOL
,
CORONARY HEART
DISEASE
  (
CHD
),
SOYBEAN APHID
,
CAROTENOIDS
,
TOCOPHEROLS
,
RHIZOBIUM
  (
BACTERIA
),
PHARMA-
COENVIROGENETICS
.
SP See
SUBSTANCE P
.
Species A single type (taxonomic group) or
organism as determined by the distinguishing
characteristics used for the particular group
of life forms (e.g., the horse is one species
among the mammals). While the horse is eas-
ily distinguished from other, obviously non-
similar mammals, such as humans (e.g., due
to the horse’s four legs vs. the human’s two
legs and two arms), it is less easy to distin-
guish a horse from a more closely related
animal such as a donkey or a zebra. The so-
called “boundary between different species”
is determined by human assessment/categori-
zation (e.g., whether systematics or cladistics
are utilized by those doing the species cate-
gorizations and definitions), and sometimes
changes when more information becomes
known at a later date (e.g., if new 2D electro-
phoresis tests reveal certain types to be genet-
ically related or not). See also 
STRAIN
,
SYSTEMATICS
,
CLADISTICS
,
CONSERVED
,
DIVERSITY
(within a species), 
ELECTROPHORESIS
,
TWO
-
DIMENSIONAL
 (
2
D
)
GEL ELECTROPHORESIS
.
Species Specific Refers to a compound (e.g.,
a protein) or a disease (e.g., a viral infection)
or some other effect that only acts in/on one
specific species of organism. For example,
the antibiotic penicillin kills bacteria by
blocking an enzyme that is critical for
growth and repair of the bacterial cell wall
(i.e., peptidoglycan layer), but penicillin
does not harm other species (e.g., man).
Bovine somatotropin is a protein hor-
mone that increases the growth rate of young
cattle and also increases the efficiency of
mature cows in converting their feed into
milk. Bovine somatotropin has no effect on
humans, and (if eaten) is simply digested
like any other food protein. It appears that
most growth hormones are species specific.
See also 
SPECIES
,
HORMONE
,
PENICILLIN G
(
BENZYLPENICILLIN
).
Specific Activity An enzyme unit defined as
the number of moles of substrate converted
to product by an enzyme preparation per unit
time under specified conditions of pH, sub-
strate concentration, temperature, etc. Spe-
cific enzyme activity units may be expressed
as: moles of product produced/minute/mg of
protein used (or mole of enzyme used if the
preparation is pure). See also 
MOLE
,
ENZYME
,
SUBSTRATE
 (
CHEMICAL
).
Spectrophotometer An instrument that mea-
sures the concentration of a compound that
has been dissolved in a solvent (water, alco-
hol, etc.). The instrument shines a light
through the solution, measures the fraction
of the light that is absorbed by the solution,
and calculates the concentration from that
absorbance value. See also 
OPTICAL DENSITY
(
OD
),
ABSORBANCE
 (
A
).
Splice Variants Refers to all possible gene
transcripts (e.g., arising from alternative
splicing). See also 
TRANSCRIPTOME
.
Splicing The removal of introns and joining of
exons in RNA (e.g., genes). Thus, introns
are spliced out, while exons are spliced
together. See also 
EXON
,
INTRON
,
GENETIC ENGI-
NEERING
,
RIBONUCLEIC ACID
  (
RNA
),
CENTRAL
DOGMA
 (
NEW
).
Splicing Junctions The sequences (in RNA
molecules) of nucleotides immediately sur-
rounding the exon-intron boundaries. See
also
EXON
,
INTRON
,
SPLICING
,
NUCLEOTIDE
.