Biotechnology

H
Highly Available Phosphate Corn (maize)
See
LOW
-
PHYTATE CORN
.
Highly Available Phosphorous (HAP) Gene
See
LOW
-
PHYTATE CORN
.
Highly Unsaturated Fatty Acids (HUFA)
Refers to a number of unsaturated fatty acids
(e.g., that the human body forms from poly-
unsaturated fatty acids it consumes in diet)
containing four or more double (molecular)
bonds; i.e., arachidonic acid, docosahex-
anoic acid, eicosapentanoic acid. These
HUFAs are utilized (by the human body) to
make prostaglandins and other eicosanoids.
See also 
POLYUNSATURATED FATTY ACIDS
(
PUFA
),
UNSATURATED FATTY ACIDS
,
ESSENTIAL
FATTY ACIDS
,
CORONARY HEART DISEASE
 (
CHD
),
N-
3
FATTY ACIDS
,
N-
6
FATTY ACIDS
,
DOCOSAHEX-
ANOIC ACID
  (
DHA
),
EICOSAPENTANOIC ACID
(
EPA
),
ARACHIDONIC ACID
 (
AA
),
PROSTAGLANDIN
ENDOPEROXIDE SYNTHASE
.
Histamine A base that is naturally present in
ergot (a fungus) and plants; it is also natu-
rally produced by basophils (basophilic leu-
kocytes) in the human body. It is formed
from histidine by decarboxylation, and is
held to be responsible for the dilation and
increased permeability of blood vessels
which play a major role in allergic reactions.
See also 
BASE
,
HISTIDINE
 (
HIS
),
BASOPHILS
.
Histidine (his) A basic amino acid that is
essential in the nutrition of the rat. It is
formed by the decomposition of most pro-
teins (as globin). See also 
PROTEIN
.
Histiocyte See
MACROPHAGE
.
Histoblasts See
B LYMPHOCYTES
.
Histones Proteins rich in basic amino acids
(e.g., lysine) found complexed with chromo-
somes of all eucaryotic cells except sperm,
where the DNA is specifically complexed
with another group of basic proteins, the
protamines. See also 
CHROMOSOMES
,
CHROMA-
TIDS
,
CHROMATIN
.
Histopathologic Refers to changes in tissue
caused by a disease. For example, certain
diseases (e.g., jaundice) cause the skin to
turn yellow. See also 
PATHOGENIC
,
VIRUS
,
CANCER
,
ADHESION MOLECULE
.
HIV-1 and HIV-2 See
HUMAN IMMUNODEFI-
CIENCY VIRUS TYPE
1
  (
HIV-
1
),
HUMAN IMMUNO-
DEFICIENCY VIRUS TYPE
2
 (
HIV-
2
).
HLA See
HUMAN LEUKOCYTE ANTIGENS
.
HNE The common chemical (by-)product of
lipid oxidation, known as 4-hydroxy-2-non-
enal, which is an aldehyde. See also 
OXIDA-
TIVE STRESS
,
OXIDATION
,
PLASMA MEMBRANE
,
LIPIDS
.
HNGF Human nerve growth factor. See also
NERVE GROWTH FACTOR
 (
NGF
).
HOC See
HIGH
-
OIL CORN
.
Hollow Fiber Separation (of proteins). The
separation of proteins from a mixture by
means of “straining” the mixture through
hollow, semipermeable fibers (e.g., polysul-
fone fibers) under pressure. The hollow
fibers are constructed in such a way that they
have very tiny (molecular size) holes in
them. In this way, large molecules are
retained in the original liquid while smaller
molecules, which are able to pass through
the holes, are filtered out. See also 
DIALYSIS
,
PROTEIN
,
ULTRAFILTRATION
.
Holoenzyme The entire, functionally com-
plete enzyme. The term is used to designate
an enzyme that requires a coenzyme in order
for it to function (possess catalytic abilities).
The holoenzyme consists of the protein part
(apoenzyme) plus a dialyzable, nonprotein
coenzyme part that is bound to the apoen-
zyme protein. See also 
COENZYME
,
APOENZYME
,
DIALYSIS
.
Homeobox A short sequence of DNA that is
180 base pairs long and located in the 3
′ exon
of certain genes of the Drosophila fly (where
they were discovered by Walter Gehring dur-
ing the 1970s). In the 1980s, Jani Christian
Nusslein-Volhard discovered that one
homeobox was attached (in adjacent exon)
to each of the genes that are responsible for
embryonic development (i.e., “switched on”
only in an embryo that is developing into an
adult), in a wide variety of species including
invertebrates, birds, and mammals. Thus, it
is now possible to locate many embryonic-
development genes in many species by using
a DNA probe (made via a Drosophila
h o m e o b o x   D NA   s e q u e n c e )   t o   fi n d
homeobox sequences attached to those
embryonic-development genes. In such a
role, the respective homeobox sequences
attached to each gene are known as DNA
markers. See also 
GENE
,
DEOXYRIBONUCLEIC
ACID
 (
DNA
),
DNA PROBE
,
DNA MARKER
,
SEQUENCE
© 2002 by CRC Press LLC

H
(
OF A DNA MOLECULE
),
BASE PAIR
 (
bp
),
DROSO-
PHILA
,
EXON
,
SPECIES
.
Homeostasis A tendency toward maintenance
of a relatively stable internal environment in
the bodies of higher animals through a series
of interacting physiological processes. An
example is the mammal’s maintenance of a
constant body temperature despite extremes
in weather temperature. See also 
SELECTINS
,
LECTINS
,
ADHESION MOLECULE
.
Homing Receptor Also known as 
L
-selectin.
See also 
SELECTINS
,
LECTINS
,
ADHESION MOLE-
CULES
.
Homologous (chemically) See
HOMOLOGY
.
Homologous (chromosomes or genes) Chro-
mosomes or chromosome segments that are
identical with respect to their constituent
sequence, genetic loci, and/or their visible
structure (in the case of chromosomes). So,
for example, a gene of “unknown” function
in humans could be compared (in a database)
with genes of a simpler organization (e.g.,
Caenorhabditus elegans). If the human gene
is homologous, and the function of the Cae-
norhabditus elegans gene is known, the
function of the human gene could be inferred
by comparison. See also 
CHROMOSOMES
,
GENE
,
SEQUENCE
  (
OF A DNA MOLECULE
),
LOCUS
,
CAENORHABDITUS ELEGANS
.
Homologous Protein A protein having identi-
cal functions and similar properties in dif-
f e r e n t   s p e c i e s .   F o r   e x a m p l e ,   t h e
hemoglobins that perform identical func-
tions in the blood of different species.
Homology A sequence of amino acids in two
or more proteins that are identical to each
other. Nucleic-acids homology refers to
complementary strands that can hybridize
with each other. See also 
TATA HOMOLOGY
,
PROTEIN
,
HYBRIDIZATION
 (
MOLECULAR GENETICS
).
Homotropic Enzyme An allosteric enzyme
whose own substrate functions as an activity
modulator. See also 
ENZYME
.
Homozygote An organism in which the corre-
sponding genes (alleles) on the two genomes
are identical. An organism which possesses
an identical pair of alleles in regard to a
given (genetic) characteristic. See also 
GENE
,
ALLELE
,
GENOME
,
GENOTYPE
,
PHENOTYPE
,
HOMOZYGOUS
,
HETEROZYGOTE
.
Homozygous In a diploid organism, a state
where both alleles of a given gene are the
same. See also 
HETEROZYGOTE
,
ALLELE
,
DIPLOID
,
DIPLOPHASE
,
HOMOZYGOTE
.
Hormone A type of chemical messenger (pep-
tide), occurring in both plants and animals,
that acts to inhibit or excite metabolic activ-
ities (in that plant or animal) by binding to
receptors on specific cells to deliver its
“message.” A hormone’s site of production
is distant from the site of biological activity
(i.e., where the message is delivered). See
also
PEPTIDE
,
MINIMIZED PROTEINS
,
SIGNALING
,
SIGNALING MOLECULE
,
ALBUMIN
.
Host Cell A cell whose metabolism is used for
growth and reproduction by a virus. Also the
cell into which a plasmid is introduced (in
recombinant DNA experiments).
Host Vector (HV) System The host is the
organism into which a gene from another
organism is transplanted. The guest gene is
carried by a vector (i.e., a larger DNA mol-
ecule, such as a plasmid, or a virus into
which that gene is inserted) which then prop-
agates in the host.
Hot Spots Sites in genes at which events, such
as mutations, occur with unusually high fre-
quency. See also 
GENE
,
JUMPING GENES
,
MUTA-
TION
,
TRANSLOCATION
.
HPLC High-performance liquid chromatogra-
phy. See also 
CHROMATOGRAPHY
.
HSOD See
HUMAN SUPEROXIDE DISMUTASE
 (
h
SOD
).
HTC See
HERBICIDE
-
TOLERANT CROP
,
STS
,
PAT
GENE
,
EPSP SYNTHASE
,
ALS GENE
,
BAR GENE
,
CP
4
EPSPS
,
GLYPHOSATE OXIDASE
.
HTS Herbicide-Tolerant Soybeans. See also
SOYBEAN PLANT
,
GLYPHOSATE
,
CP
4
EPSPS
,
EPSP
SYNTHASE
,
GLYPHOSATE OXIDASE
,
HERBICIDE
-
TOLERANT CROP
,
STS
,
GLUFOSINATE
,
PAT GENE
,
BAR GENE
.
HTS See
HIGH
-
THROUGHPUT SCREENING
 (
HTS
).
Human Artificial Chromosomes (HAC)
Chromosomes that have been synthesized
(made) from chemicals that are identical to
chromosomes within human cells. See also
YEAST ARTIFICIAL CHROMOSOMES
 (
YAC
),
BACTE-
RIAL ARTIFICIAL CHROMOSOMES
 (
BAC
),
CHROMO-
SOMES
,
ARABIDOPSIS THALIANA
,
SYNTHESIZING
 (
OF
DNA MOLECULES
).
Human Chorionic Gonadotropin A human
hormone. In 1986, Mark Bogart discovered
© 2002 by CRC Press LLC

H
that elevated levels of human chorionic
gonadotropin in pregnant women are corre-
lated with babies (later) born with Down
syndrome. See also 
HORMONE
.
Human Colon Fibroblast Tissue Plasmino-
gen Activator A second generation tissue
plasminogen activator (tPA), which has the
clot-sensitive activation of plasminogen with
potentially greater selectivity and (clot)
specificity. See also 
TISSUE PLASMINOGEN ACTI-
VATOR
 (
t
PA
).
Human EGF-Receptor-Related Receptor
(HER-2) A gene that appears to be directly
related to human breast cancer mortality.
The more copies of the HER-2 gene (in a
patient’s breast tumor cells), the more dismal
that patient’s prospects for survival.
Human Embryonic Stem Cells Those cells
(in the early embryo’s inner cell mass) from
which each of the human body’s 210 differ-
ent types of tissues arise via differentiation,
proliferation, and growth processes. See also
PLURIPOTENT
,
STEM CELL GROWTH FACTOR
 (
SCF
),
DIFFERENTIATION
.
Human Gamma-Glutamyl Transpeptidase
A glycoprotein that is thought to possess a
different oligosaccharide when it is pro-
duced by a (liver) tumor cell instead of a
healthy cell. Thus, it is a possible early warn-
ing marker for liver cancer. See also 
GLYCO-
PROTEIN
,
OLIGOSACCHARIDES
.
Human Growth Hormone (HGH) S e e
GROWTH HORMONE
 (
GH
).
Human Immunodeficiency Virus Type 1
(HIV-1) One of the two “families” of the
viruses identified (so far) which cause
acquired immune deficiency syndrome
(AIDS), although not all strains of HIV-2
cause AIDS. HIV-1 and HIV-2 show a pref-
erential tropism (affinity) toward the helper
T cells, although other immune system (and
nervous system) cells are also infected. The
GP120 envelope (surface) protein of HIV-1
and HIV-2 directly interacts (binds) with the
CD4 proteins (receptors) on the surface of
helper T cells, enabling the viruses to bind
(attach to) and infect the helper T cells.
In order to successfully enter and infect
cells, the HIV must also bind with CKR-5
proteins (receptors) located on the surface of
cells of most humans. In 1996, Nathaniel
Landau and Richard Koup discovered that
approximately 1% of humans carry a gene
for a version of CKR-5 receptor that resists
entry to cells by HIV. As of 1996, a total of
nine separate strains (serotypes) of human
immunodeficiency virus were known; iden-
tified by the letters A, B, C, D, E, F, G, H,
I. See also 
CD
4
PROTEIN
,
TAT
,
TATA HOMOLOGY
,
ADHESION MOLECULE
,
GP
120
PROTEIN
,
ACQUIRED
IMMUNE DEFICIENCY SYNDROME
  (
AIDS
),
RECEP-
TORS
,
TROPISM
,
HELPER T CELLS
  (
T
4
CELLS
),
STRAIN
,
T CELL RECEPTORS
,
VIRUS
,
SEROTYPES
,
HUMAN IMMUNODEFICIENCY VIRUS TYPE
2
(
HIV-
2
).
Human Immunodeficiency Virus Type 2
(HIV-2) See
H U M A N I M M U N O D E F I C I E N C Y
VIRUS TYPE
1
 (
HIV-
1
).
Human Leukocyte Antigens (HLA) A very
complex array of six proteins that cover the
surface of leukocytes (and the bone marrow
cells that produce leukocytes). These HLA
are usually different (i.e., a nonmatch) for
individuals that are not genetically related to
each other (e.g., a father-son or a father-
daughter), so have been used in the past to
prove paternity. HLA must also be matched
(as nearly as possible) for successful bone
marrow transplants, to prevent the donated
bone marrow (and the marrow recipient)
from “rejecting” each other. See also 
LEUKO-
CYTES
,
ANTIGEN
,
MAJOR HISTOCOMPATIBILITY
COMPLEX
  (
MHC
),
PROTEIN
,
GRAFT
-
VERSUS
-
HOST
DISEASE
 (
GVHD
).
Human Protein Kinase C An enzyme that is
involved in the control of blood coagulation
and fibrinolysis. See also 
FIBRIN
.
Human Superoxide Dismutase (hSOD) A n
enzyme that “captures” oxygen free radicals
(oxygen atoms bearing an extra electron,
thus high in energy: e.g., which are some-
times generated in a biological system such
as within the body of an organism). Oxygen
free radicals are generated within occluded
blood vessels when a blood clot blocks arter-
ies in the heart, causing a heart attack. These
oxygen free radicals are highly energized
and can cause damage to blood vessel walls
after the clot is dissolved (e.g., with tissue
plasminogen activator), so hSOD may prof-
itably be administered in conjunction with
clot-dissolving pharmaceuticals to minimize
© 2002 by CRC Press LLC

H
damage when occluded arteries are
reopened.
Research indicates that hSOD may help
protect elderly patients from the lethal
effects of influenza (the flu), because influ-
enza often causes overproduction of free rad-
icals in the victim’s body. Recent research
indicates that hSOD may be made more
effective when administered in combination
with certain copper/zinc compounds to bol-
ster its efficacy. See also 
FREE RADICAL
,
PEG
-
SOD
  (
POLYETHYLENE GLYCOL SUPEROXIDE DIS-
MUTASE
),
CATALASE
,
XANTHINE OXIDASE
,
TISSUE
PLASMINOGEN ACTIVATOR
 (
t
PA
),
ANTIOXIDANTS
.
Human Thyroid-Stimulating Hormone
(hTSH) A naturally occurring hormone that
causes the thyroid gland to develop. See also
HORMONE
.
Humoral Immune Response Refers to the
rapid manufacture and secretion by the body
of the soluble blood serum components —
e.g., antibodies (by B cells), complement
proteins, cecrophins, etc. — in response to
an infection. See also 
ANTIBODY
,
COMPLEMENT
,
COMPLEMENT CASCADE
,
CECROPHINS
,
HUMORAL
IMMUNITY
.
Humoral Immunity The immune system
response consisting of the soluble blood
serum components that fight an infection
(antibodies, complement proteins, cecrophins,
etc.). See also 
ANTIBODY
,
COMPLEMENT
,
COM-
PLEMENT CASCADE
,
CECROPHINS
,
CELLULAR
IMMUNE RESPONSE
,
IMMUNOGLOBULIN
.
HuSNPs Abbreviation for Human SNPs (sin-
gle-nucleotide polymorphisms). See also
SINGLE
-
NUCLEOTIDE POLYMORPHISMS
 (
SNP
s
).
Hybrid Vigor See
F
1
HYBRIDS
,
HYBRIDIZATION
(
PLANT GENETICS
).
Hybridization (molecular genetics) The pair-
ing (tight physical bonding) of two comple-
mentary single strands of RNA and/or DNA
to give a double-stranded molecule. See also
ANNEAL
,
STICKY ENDS
,
RIBONUCLEIC ACID
 (
RNA
),
MESSENGER RNA
  (
m
RNA
),
BIOSENSORS
  (
ELEC-
TRONIC
),
BIOSENSORS
 (
CHEMICAL
),
HYBRIDIZATION
SURFACES
,
DNA PROBE
,
DEOXYRIBONUCLEIC ACID
(
DNA
),
ANTISENSE
 (
DNA SEQUENCE
),
BIOMOTORS
.
Hybridization (plant genetics) The mating
of two plants from different species or genet-
ically very different members of the same
species to yield hybrids (first filial hybrids)
possessing some of the characteristics of
each parent. Those (hybrid) offspring tend
to be more healthy, productive, and uniform
than their parents — a phenomenon known
as “hybrid vigor.” Hybrids can also arise
from more than two (“parent”) species.
Hybrid corn/maize seed was first commer-
cialized (in the U.S.) in 1922. Other recently
created crop hybrids include tangelos (pro-
duced by crossing grapefruit with tanger-
ines), nectarines (bred from peaches), and
brocciflower (produced by crossing broccoli
with cauliflower).
Some hybrids have occurrred spontane-
ously in nature. For example, wheat (Triticum
aestivum) arose centuries ago from a naturally
occurring interbreeding of three Middle East
grasses. In the 1980s, sugar beet (Beta vul-
garis, subspecies vulgaris) naturally interbred
with the wild native weed known as sea beet
(Beta vulgaris, subspecies maritima) in
Europe, resulting in an annual weed (in con-
trast to sugar beet, which is a biannual).
Because that new hybrid weed is closely
related to sugar beet, any herbicide that kills
the new hybrid weed is likely to harm the
sugar beet crop (unless the sugar beet crop is
made herbicide-tolerant). See also 
F
1
HYBRIDS
,
SPECIES
,
TRANSGRESSIVE SEGREGATION
,
GENETICS
,
CORN
,
WHEAT
,
GEM
,
EXOTIC GERMPLASM
,
BAR-
NASE
,
HERBICIDE
-
TOLERANT CROP
.
Hybridization Surfaces Va r i o u s   p h y s i c a l
substrates (surfaces) onto which have been
“attached” genetic materials (DNA, RNA,
oligonucleotides, etc.). Relevant comple-
mentary genetic materials (DNA, RNA, oli-
gonucleotides, etc.) then are hybridized onto
those attached-to-surface genetic materials
for various specific purposes (e.g., detection
of the presence of those unattached genetic
materials, in the case of biosensor’s hybrid-
ization surface). One of the technologies that
can be utilized to assay (evaluate) DNA from
hybridization surfaces is Matrix-Assisted
Laser Desorption Ionization Time of Flight
Mass Spectrometry (MALDI-TOF-MS). See
also
SUBSTRATE
  (
STRUCTURAL
),
HYBRIDIZATION
(
MOLECULAR GENETICS
),
COMPLEMENTARY DNA
(
c
-
DNA
),
DEOXYRIBONUCLEIC ACID
 (
DNA
),
RIBO-
NUCLEIC ACID
 (
RNA
),
NANOCRYSTAL MOLECULES
,
DOUBLE HELIX
,
BIOSENSORS
  (
ELECTRONIC
),
© 2002 by CRC Press LLC

H
BIOSENSORS
 (
CHEMICAL
),
BIOCHIPS
,
OLIGONUCLE-
OTIDE
,
OLIGONUCLEOTIDE PROBES
,
MALDI
-
TOF
-
MS
,
ASSAY
,
MICROARRAY
 (
TESTING
).
Hybridoma The cell line produced by fusing
a myeloma (tumor cell) with a lymphocyte
(which makes antibodies); it continues
indefinitely to express the immunoglobulins
(antibodies) of both parent cells. See also
MONOCLONAL ANTIBODY
 (
MA
b
),
AGING
.
Hydrazine A chemical with formula N
2
H
4
.
Used as a rocket fuel, and in the hydrazinol-
ysis of glycoproteins. See also 
HYDRAZINOLY-
SIS
 (
OF GLYCOPROTEINS
,
TO ISOLATE UNREDUCED
OGLIOSACCHARIDE SIDE CHAINS
),
GLYCOPROTEIN
,
REDUCTION
 (
IN A CHEMICAL REACTION
).
Hydrazinolysis (of glycoproteins to isolate
unreduced oligosaccharide side chains) A
technique that used the chemical hydrazine
to separate and isolate the oligosaccharide
portion from the protein portion of a glyco-
protein. The hydrazine chemically “chews
up” the polypeptide (i.e., protein) portion of
a glycoprotein molecule, leaving the intact
oligosaccharides behind. It can subse-
quently be analyzed (after chromatographic
separation from the peptide pieces and other
chemical components). See also 
REDUCTION
(
IN A CHEMICAL REACTION
),
HF CLEAVAGE
,
P O L Y P E P T I D E
  (
P R O T E I N
),
G L Y C O P R O T E I N
,
SEQUENCING
  (
OF OLIGOSACCHARIDES
),
HYDRA-
ZINE
,
CHROMATOGRAPHY
.