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 polyunsaturated fatty acids it consumes in diet) containing four or more double (molecular) bonds; i.e., arachidonic acid, docosahexanoic 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 naturally produced by basophils (basophilic leukocytes) 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 proteins (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 chromosomes 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 IMMUNODEFICIENCY 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., polysulfone fibers) under pressure. The hollow fibers are constructed in such a way that they

have very tiny (molecular size) holes in H 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 complete 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 apoenzyme 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 during 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 embryonicdevelopment 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

(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.

HHomologous (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 Caenorhabditus 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 identical 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 functions 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 corresponding 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 (peptide), occurring in both plants and animals, that acts to inhibit or excite metabolic activities (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 molecule, such as a plasmid, or a virus into which that gene is inserted) which then propagates 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, MUTATION, TRANSLOCATION.

HPLC High-performance liquid chromatogra-

phy. See also CHROMATOGRAPHY.

HSOD See HUMAN SUPEROXIDE DISMUTASE (hSOD).

HTC See HERBICIDE-TOLERANT CROP, STS, PAT

GENE, EPSP SYNTHASE, ALS GENE, BAR GENE, CP4

EPSPS, GLYPHOSATE OXIDASE.

HTS Herbicide-Tolerant Soybeans. See also

SOYBEAN PLANT, GLYPHOSATE, CP4 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

that elevated levels of human chorionic gonadotropin in pregnant women are correlated with babies (later) born with Down syndrome. See also HORMONE.

Human Colon Fibroblast Tissue Plasminogen 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 ACTIVATOR (tPA).

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 different 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 produced by a (liver) tumor cell instead of a healthy cell. Thus, it is a possible early warning 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 preferential 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; identified by the letters A, B, C, D, E, F, G, H,

I. See also CD4 PROTEIN, TAT, TATA HOMOLOGY,

ADHESION MOLECULE, GP120 PROTEIN, ACQUIRED

IMMUNE DEFICIENCY SYNDROME (AIDS), RECEP-

TORS, TROPISM, HELPER T CELLS (T4 CELLS),

STRAIN, T CELL RECEPTORS, VIRUS, SEROTYPES,

HUMAN IMMUNODEFICIENCY VIRUS TYPE 2

(HIV- 2).

Human Immunodeficiency Virus Type 2	H
(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

damage when occluded arteries are reopened.

Research indicates that hSOD may help protect elderly patients from the lethal effects of influenza (the flu), because influenza often causes overproduction of free radicals 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 bolster its efficacy. See also FREE RADICAL, PEG-

SOD (POLYETHYLENE GLYCOL SUPEROXIDE DIS-

MUTASE), CATALASE, XANTHINE OXIDASE, TISSUE

PLASMINOGEN ACTIVATOR (tPA), ANTIOXIDANTS.

HHuman 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 (SNPs).

Hybrid Vigor See F1 HYBRIDS, HYBRIDIZATION

(PLANT GENETICS).

Hybridization (molecular genetics) The pairing (tight physical bonding) of two complementary single strands of RNA and/or DNA to give a double-stranded molecule. See also

ANNEAL, STICKY ENDS, RIBONUCLEIC ACID (RNA),

MESSENGER RNA (mRNA), 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 genetically 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 commercialized (in the U.S.) in 1922. Other recently created crop hybrids include tangelos (produced by crossing grapefruit with tangerines), nectarines (bred from peaches), and brocciflower (produced by crossing broccoli with cauliflower).

Some hybrids have occurrred spontaneously 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 vulgaris, 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 contrast 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 F1 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 complementary genetic materials (DNA, RNA, oligonucleotides, 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 hybridization 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