Biotechnology

MCA See
MEDICINES CONTROL AGENCY
 (
MCA
).
MEA Acronym for Multilateral Environmental
Agreement; an agreement (treaty) between
a number of nations intended to protect/ben-
efit the environment. See also 
CONVENTION ON
BIOLOGICAL DIVERSITY
 (
CBD
).
Medicines Control Agency (MCA) The Brit-
ish Government agency that, in concert with
the Committee on Safety in Medicines, reg-
ulates the approval and sale of pharmaceu-
tical products in the United Kingdom. See
also
COMMITTEE ON SAFETY IN MEDICINES
,
FOOD
AND DRUG ADMINISTRATION
  (
FDA
),
COMMITTEE
FOR PROPRIETARY MEDICINAL PRODUCTS
 (
CPMP
),
KOSEISHO
,
NDA
 (
TO KOSEISHO
),
IND
,
BUNDESGE-
SUNDHEITSAMT
 (
BGA
).
Medifoods See
NUTRACEUTICALS
,
PHYTOCHEMI-
CALS
.
Medium A substance used to provide nutrients
for cell growth. It may be liquid (e.g., broth)
or solid (e.g., agar). See also 
CULTURE
MEDIUM
,
AGAR
,
MAMMALIAN CELL CULTURE
.
Mega-Yeast Artificial Chromosomes (mega
YAC) A large (greater than 500 base pairs
in length) piece of DNA that has been cloned
(made) inside a living yeast cell. While most
bacterial vectors cannot carry DNA pieces
that are larger than 50 base pairs, and “stan-
dard” YACs typically cannot carry DNA
pieces that are larger than 500 base pairs,
mega YACs can carry DNA pieces (chromo-
somes) as large as one million base pairs in
length. See also 
YEAST
,
CHROMOSOMES
,
HUMAN
ARTIFICIAL CHROMOSOMES
  (
HAC
),
ARABIDOPSIS
© 2002 by CRC Press LLC

M
THALIANA
,
DEOXYRIBONUCLEIC ACID
  (
DNA
),
CLONE
  (
A MOLECULE
),
VECTOR
,
BASE PAIR
  (
bp
),
YEAST ARTIFICIAL CHROMOSOMES
 (
YAC
).
Megakaryocyte Stimulating Factor (MSF)
A colony stimulating factor (protein)
involved in the regulation of platelet produc-
tion, white blood cell production, and red
blood cell production from stem cells in
bone marrow. See also 
COLONY STIMULATING
FACTORS
 (
CSF
s
),
PLATELETS
,
STEM CELLS
.
Meiosis Discovered by Edouard Van Beneden
in the 1870s, meiosis is the sequence of com-
plex cell nucleus changes resulting in the
production of cells (as gametes) with half
the number of chromosomes present in the
original cell. It typically involves an actual
reduction division in which the chromo-
somes without undergoing prior splitting
join in pairs with homologous chromosomes
(of maternal and paternal origin) and then
separate (i.e., pulled apart by microtubules
within the cell), so that one member of each
pair enters each product cell nucleus and
undergoes a second division not involving
reduction. Occurs by two successive divi-
sions (meiosis I and II) that reduce the start-
ing number of 4n chromosomes to 1n in each
of four product cells. Product cells may
mature to germ cells (sperm or eggs). See
also
OOCYTES
,
CELL
,
CHROMOSOME
,
NUCLEUS
,
MICROTUBULES
.
Melting (of DNA) Melting DNA means to
heat-denature it. When this happens, the
hydrogen bonds holding the DNA molecule
together in the normal way are disrupted,
allowing a more random polymer structure
to exist. See also 
DENATURED DNA
.
Melting (of substance other than DNA) To
change from a solid to a nonsolid (e.g., liq-
uid) state by the addition of heat (to the solid
substance).
Melting Temperature (of DNA) (Tm) T h e
midpoint of the temperature range over
which DNA is denatured. See also 
MELTING
(
OF DNA
).
Membrane Transport The facilitated transport
of a solute across a membrane, usually by a
specific membrane protein (e.g., adhesion
molecule). See also 
ENDOCYTOSIS
,
EXOCYTOSIS
,
SIGNAL TRANSDUCTION
,
G-PROTEINS
,
VAGINOSIS
,
RECEPTORS
,
ADHESION MOLECULE
,
VESICULAR
TRANSPORT
,
GATED TRANSPORT
,
CALCIUM CHAN-
NEL
-
BLOCKERS
.
Membrane Transporter Protein A class of
transmembrane proteins (i.e., protein mole-
cules embedded in a cell’s membrane,
extending through both sides of the mem-
brane) that function to transport certain mol-
ecules through the cell’s membrane. Such
molecules which are thus “transported”
include: sugar molecules (utilized by the cell
as “fuel”); inorganic ions (which catalyze
certain cellular processes); polypeptides
[e.g., “manufactured” in the cell’s ribo-
some(s) and then secreted from the cell to
perform some function elsewhere in the
body of the organism]; anticancer drugs;
antibiotics. See also 
PROTEIN
,
CELL
,
PLASMA
MEMBRANE
,
MEMBRANE TRANSPORT
,
RIBOSOMES
,
POLYPEPTIDE
 (
protein
),
ABC TRANSPORTERS
.
Membranes (of a cell) Refers to the thin
“skin-like” structures that surround the exte-
rior of a cell (i.e., plasma membrane), and
also surround various specialized bodies
(nucleus, mitochondria, etc.) within the cell
itself (e.g., the membrane that surrounds the
cell’s nucleus is called the “nuclear enve-
lope”). Membranes are lipoidal, i.e., made
of fat-like material, in which proteins and
protein complexes are embedded. For exam-
ple, protein molecules known as receptors
are embedded in the plasma membrane (i.e.,
the outermost membrane of the cell) and in
the nuclear envelope. See also 
CELL
,
CECROPHINS
  (
LYTIC PROTEINS
),
MAGAININS
,
PLASMA MEMBRANE
,
TRANSMEMBRANE PROTEINS
,
ION CHANNELS
,
RECEPTORS
,
NUCLEAR RECEPTORS
.
MEMS (nanotechnology) Acronym utilized
by Americans to refer to “micro-electrome-
chanical systems” (which Europeans tend to
refer to as “microsystems technology” —
MST). See also 
NANOTECHNOLOGY
,
BIOCHIP
,
GENOSENSORS
,
BIOSENSORS
  (
ELECTRONIC
),
BIO-
SENSORS
 (
CHEMICAL
),
NANOCRYSTAL MOLECULES
MICROFLUIDICS
,
QUANTUM WIRE
,
QUANTUM DOT
,
MOLECULAR MACHINES
,
BIOMOTORS
,
BIOMEMS
.
mEPSPS The “m” variant (of the many forms
of) the enzyme 5-enolpyruvyl-shikimate-3-
phosphate synthase. mEPSPS is unaffected
by glyphosate- or sulfosate-containing
herbicides, so introduction of the gene (cod-
ing for mEPSPS) into crop plants (e.g.,
© 2002 by CRC Press LLC

M
corn/maize) makes those crop plants essen-
tially impervious to glyphosate- or sulfosate-
containing herbicides. See also 
ENZYME
,
GENE
,
GENETIC ENGINEERING
,
EPSP SYNTHASE
,
GLYPHOSATE
,
SULFOSATE
,
CORN
,
HERBICIDE
-
TOL-
ERANT CROP
,
ARO A
.
Mesenchymal Adult Stem Cells See
M E S O -
DERMAL ADULT STEM CELLS
.
Mesodermal Adult Stem Cells Certain stem
cells present within (adult) bodies of organ-
isms, that can be differentiated (via chemical
signals) to give rise to bone, muscle, and/or
fat cells. See also 
STEM CELLS
,
MULTIPOTENT
ADULT STEM CELLS
,
CELL
,
ORGANISM
,
SIGNALING
.
Mesophile An organism that grows best in the
temperature range of 25°C (77°F) to 40°C
(104°F). See also 
THERMOPHILE
,
PSYCHROPHILE
.
Messenger”_Molecule_See_SIGNALING_MOLE-_CULE_,_HORMONE_,_NITRIC_OXIDE_._Messenger_RNA_(mRNA)'>“Messenger” Molecule See
SIGNALING MOLE-
CULE
,
HORMONE
,
NITRIC OXIDE
.
Messenger RNA (mRNA) Messenger ribo-
nucleic acid. The intermediary molecule
between DNA and ribosomes (in a cell)
which synthesize (manufacture) those pro-
teins coded for by the cell’s DNA. Upon
receiving the “message” encoded in the
DNA, the messenger RNA passes through
the ribosomes like a reel of punched paper
passes through an old player piano (pianola),
giving the ribosomes the specifications for
making the coded-for proteins. This process
is aided by transfer RNA (tRNA) molecules,
which forage for amino acids that float
around in the cell (outside of the cell’s
nucleus and ribosomes). The transfer RNA
(tRNA) molecules attach to, and escort, indi-
vidual amino acids to the ribosome, as and
when the messenger RNA (mRNA) directs.
Each of the 20 different amino acids has at
least one of its own purpose-built tRNA mol-
ecules, which possess a three-letter code of
nucleotides at the stem of the cloverleaf-
shaped rRNA molecule.
The ribosome has room for only two
tRNA molecules at a time. The messenger
RNA (mRNA) molecule (which itself is
passing through the ribosome) calls over the
first tRNA molecule, which brings with it
the specified amino acid. Short sections of
the messenger RNA (mRNA) and transfer
RNA (tRNA) molecules lock together inside
the ribosome (because where these two mol-
ecules meet, their three nucleotides are com-
plementary), the whole (locked together)
apparatus shifts along by three notches (i.e.,
nucleotides), and a second tRNA molecule
(bearing another amino acid) slips in next to
the first tRNA molecule.
Next, the first amino acid (brought in by
the first tRNA molecule) jumps over to the
second tRNA molecule, joining to the amino
acid that was brought in by the second tRNA
molecule, thus making the start of a protein
(i.e., a poly-amino acid molecule, also
known as polypeptide or protein molecule).
The empty (first) tRNA molecule falls out
of the ribosome, and the whole (locked
together) apparatus (i.e., mRNA plus second
tRNA molecule) moves three more notches
(i.e., nucleotides) along the mRNA molecule
to make room for a third tRNA molecule
bearing another amino acid, and so on.
This process of creating ever-longer
chains of amino acids continues to repeat
itself inside the ribosome until the protein
(coded for by the DNA, which code was
transferred to mRNA, which transferred it to
the ribosome) is completed. See also 
TRAN-
SCRIPTION
,
COMPLEMENTARY DNA
 (
c-
DNA
),
CEN-
TRAL DOGMA
,
DEOXYRIBONUCLEIC ACID
  (
DNA
),
RIBONUCLEIC ACID
 (
RNA
),
NUCLEIC ACIDS
,
COD-
ING SEQUENCE
,
GENETIC CODE
,
CELL
,
INFORMA-
TIONAL MOLECULES
,
CODON
,
RIBOSOMES
,
POLYRIBOSOME
  (
POLYSOME
),
r
RNA
  (
RIBOSOMAL
RNA
),
NUCLEOTIDE
,
POLYMER
,
TRANSFER RNA
(
t
RNA
),
PROTEIN
,
AMINO ACID
,
POLYPEPTIDE
(
PROTEIN
),
ANTISENSE
 (
DNA SEQUENCE
).
Messenger
TM
See
HARPIN
.
Metabolic Engineering The selective, delib-
erate alteration of an organism’s metabolic
pathway(s) via genetic engineering of the
genes that define/control the organism’s
metabolism. Some reasons to do metabolic
engineering of an organism include:
• Altering cell “behavior” and organism
metabolic patterns to induce production
of proteins/polypeptides and/or metab-
olites that are desired by mankind (e.g.,
“golden rice”).
© 2002 by CRC Press LLC

M
• Altering cell “behavior” and organism
metabolic patterns to induce a given
organism to consume or accumulate
toxic wastes or valuable materials (e.g.,
gold) that are present at a site in low
concentration or highly dispersed.
• Altering cell “behavior” and organism
metabolic patterns to cure disease.
See also 
METABOLISM
,
INTERMEDIARY METABO-
LISM
,
CELL
,
PATHWAY
,
METABOLIC PATHWAY
,
GENETIC ENGINEERING
,
ORGANISM
,
GENE
,
GENE
SPLICING
,
PROTEIN
,
PHYTO
-
MANUFACTURING
,
POLYPEPTIDES
,
BIOLEACHING
,
BIODESULFURIZA-
TION
,
BIORECOVERY
,
BIOREMEDIATION
,
GOLDEN
RICE
,
PHYTOREMEDIATION
.
Metabolic Pathway Refers to a particular path-
way [i.e., series of chemical reactions, each of
which is dependent on previous one(s)] within
the overall process of metabolism in an organ-
ism. For example, when humans consume the
herb known as Saint John’s Wort (Hypericum
perforatum), certain components in that herb
induce a (new) metabolic pathway — cata-
lyzed by cytochrome P450 enzymes — that
(more) rapidly metabolizes (i.e., breaks down)
a number of commercial pharmaceuticals
(thereby lowering the effectiveness of a given
dose of that particular pharmaceutical). See
also
METABOLISM
,
PATHWAY
,
ORGANISM
,
INTER-
MEDIARY METABOLISM
,
CYTOCHROME
p450
,
CYTO-
CHROME
P4503A4
,
CATALYST
,
GOLDEN RICE
.
Metabolism The entire set of enzyme-catalyzed
transformations of organic nutrient molecules
(to sustain life) in living cells. Conversion of
food and water into nutrients that can be used
by the body’s cells, and the use of those nutri-
ents by those cells (to sustain life, grow, etc.).
See also 
ENZYME
,
CELL
,
INTERMEDIARY METABO-
LISM
,
METABOLITE
,
COMBINATORIAL BIOLOGY
,
CIT-
RIC ACID
,
AFLATOXIN
,
FUSARIUM
,
CYTOCHROME
P4503A4
,
PATHWAY
,
METABOLIC PATHWAY
.
Metabolite A chemical intermediate in the
enzyme-catalyzed chemical reactions of
metabolism. See also 
METABOLISM
,
ENZYME
,
CELL
,
INTERMEDIARY METABOLISM
,
AFLATOXIN
,
FUSARIUM
.
Metalloenzyme An enzyme having a metal
ion as its prosthetic group. See also 
ENZYME
,
PROSTHETIC GROUP
,
METALLOPROTEINS
.
Metalloproteins A term that is utilized to refer
to any protein molecule that contains within
it (i.e., in “peptide chain”) a metal atom
(zinc, iron, copper, etc.). Approximately one
third of all proteins are metalloproteins.
Those that contain a zinc atom (Zn
2+
) are
generally enzymes (thus called metalloen-
zymes), because that metal acts as a catalyst.
See also 
PROTEIN
,
PEPTIDE
,
ENZYME
,
CATALYST
,
METALLOENZYME
.
Metamodel Methods (of Bioinformatics)
These refer to methods utilized to integrate
data that has been independently gener-
ated/created (and generally stored in separate
database models) via independent genomics
research projects, combinatorial chemistry
projects, high-throughput screening projects
(e.g., via biochip use), etc. Metamodel meth-
ods sometimes reveal important interrelation-
ships that were not apparent in the individual
models (i.e., created solely for the genomics
project data, or created solely for the combi-
natorial chemistry project data, or created
solely for the high-throughput screening
project data, etc.). See also 
BIOINFORMATICS
,
GENOMICS
,
FUNCTIONAL GENOMICS
,
STRUCTURAL
GENOMICS
,
COMBINATORIAL CHEMISTRY
,
HIGH
-
THROUGHPUT SCREENING
,
BIOCHIP
.
Metastasis The process via which a given can-
cer (e.g., initial tumor) spreads from the site
of its initial formation (in body) to other
parts of the body. See also 
CANCER
,
OLIGOSAC-
CHARIDES
,
LECTINS
,
ANGIOGENESIS
,
GENISTEIN
(
Gen
),
ISOFLAVONES
.
Meter A unit of measurement that was con-
trived by French scientists during the 1670s.
It was initially defined to be one ten-mil-
lionth of the distance from the earth’s equa-
tor to its poles. See also 
NANOMETERS
 (
NM
).
Methionine (met) An essential amino acid;
furnishes (to organism) both labile methyl
groups and sulfur necessary for normal
metabolism. See also 
ESSENTIAL AMINO ACIDS
,
METABOLISM
,
CYSTINE
,
HIGH
-
METHIONINE CORN
.
Methyl Jasmonate The volatile chemical
compound that results when methyl groups
(CH
3
) are chemically added to a molecule of
jasmonic acid. See also 
JASMONIC ACID
.
Methyl Salicylate The volatile chemical com-
pound that results when methyl groups
© 2002 by CRC Press LLC

M
(CH
3
) are added to a molecule of salicylic
acid. During 1997, Ilya Raskin showed that
methyl salicylate emitted by one tobacco
plant (e.g., under ‘attack’ by insects, fungi,
bacteria, or viruses) could cause other
nearby tobacco plants to “turn on” their self-
defense mechanism (systemic acquired
resistance). See also 
SALICYLIC ACID
 (
SA
),
BAC-
TERIA
,
SYSTEMIC ACQUIRED RESISTANCE
  (
SAR
),
FUNGUS
.
Methylated Refers to a DNA molecule that is
saturated with methyl groups (i.e., methyl
submolecule groups, -CH
3
, have attached
themselves to the DNA molecule at all pos-
sible locations). Generally, when a DNA
molecule is methylated, the genes compris-
ing that DNA molecule are “turned off”
(inactivated). See also 
DNA METHYLATION
,
DEOXYRIBONUCLEIC ACID
 (
DNA
),
TRANSCRIPTION
,
MESSENGER RNA
  (
m
RNA
),
GENE
,
GENETIC CODE
,
p53
GENE
,
TUMOR
-
SUPPRESSOR GENES
.
MHC See
MAJOR HISTOCOMPATIBILITY COMPLEX
(
MHC
).
Micelle The spherical structure formed by the
association of a number of amphiphilic mol-
ecules dissolved in water. Structurally, the
outer surface of the micelle (sphere) is cov-
ered with the polar domains (head groups)
which are directed toward (stick into) the
water while the interior of the micelle con-
tains the nonpolar domains (tails), which
self-associate to create an “oil droplet”
microenvironment. Micelles may be used to
solubilize nonwater (oil) soluble or sparingly
water soluble molecules in water. They may
be formed by ionic or nonionic surfactants.
See also 
AMPHIPHILIC MOLECULES
,
SUPERCRITI-
CAL CARBON DIOXIDE
,
CRITICAL MICELLE CON-
C E N T R A T I O N
,
R E V E R S E
M I C E L L E
  (
R M
) ,
SURFACTANT
,
FATS
,
SELF
-
ASSEMBLY
.
Micro Sensors See
BIOCHIP
,
MICROARRAY
 (
TEST-
ING
),
BIOSENSOR
.
Micro Total Analysis Systems A b b r ev i a t e d
mTAS. See also 
GENE EXPRESSION ANALYSIS
,
BIOCHIP
,
GENOSENSORS
,
NANOTECHNOLOGY
,
BIO-
SENSORS
 (
ELECTRONIC
),
BIOSENSORS
 (
CHEMICAL
).
Micro-electromechanical Systems See
MEMS
(
NANOTECHNOLOGY
).
Microaerophile An organism that grows best
in the presence of a small amount of oxygen.
See also 
ORGANISM
,
MICROORGANISM
,
FACULTA-
TIVE ANAEROBE
.
Microarray (testing) Refers to a piece of
glass, plastic, or silicon onto which has been
placed a large number of biosensors. These
microarrays (sometimes called “biochips” or
“DNA chips”) can then be utilized to test a
single biological sample for a variety of
attributes or effects. For example, by placing
protein-detection molecules (e.g., ligands,
which change color or cause electronic sig-
nal upon contact with specific protein mol-
ecules) onto a microarray, a scientist can
perform gene expression analysis (i.e., eval-
uation of the protein expression and expres-
sion levels of genes in a biological sample).
Another application would be to place
(cellular) receptors, nucleic acids/probes,
adhesion molecules, messenger RNA (spe-
cific to which gene is “turned on” in a given
disease state), cDNA (complementary to
mRNA coded for by each gene that is
“turned on”), or cells (indicating which cel-
lular pathway is “turned on,” etc.) onto a
microarray, to utilize that microarray to
screen for proteins or other chemical com-
pounds that act against a disease (i.e., ther-
apeutic target); as indicated by (the relevant
component from biological sample) adhe-
sion or hybridization to the specific spot on
the microarray where a specific (target mol-
ecule) was earlier placed/attached. “Quan-
tum dots” could potentially be used on
microarrays in place of cellular receptors in
the future. See also 
DNA CHIP
,
BIOCHIP
,
GENE
,
CODING SEQUENCE
,
GENE EXPRESSION
,
GENE
EXPRESSION ANALYSIS
,
GENOSENSORS
,
NANO-
TECHNOLOGY
,
GENOMICS
,
FUNCTIONAL GENOM-
ICS
,
BIOSENSORS
  (
ELECTRONIC
),
BIOSENSORS
(
CHEMICAL
),
HIGH
-
THROUGHPUT SCREENING
(
HTS
),
TARGET
-
LIGAND INTERACTION SCREENING
,
RECEPTORS
,
BIORECEPTORS
,
COMBINATORIAL
CHEMISTRY
,
TARGET
 (
OF A THERAPEUTIC AGENT
),
TARGET
 (
OF A HERBICIDE OR INSECTICIDE
),
ADHE-
SION MOLECULE
,
MICROFLUIDICS
,
BIOELECTRON-
ICS
,
ASSAY
,
BIOASSAY
,
MESSENGER RNA
 (
m
RNA
),
CHARACTERIZATION ASSAY
,
PROBE
,
HYBRIDIZA-
TION
  (
MOLECULAR BIOLOGY
),
BIOINFORMATICS
,
HYBRIDIZATION SURFACES
,
PATHWAY
,
DEOXY-
RIBONUCLEIC ACID
  (
DNA
),
QUANTUM DOT
,
PRO-
TEOME CHIP
.
© 2002 by CRC Press LLC