SEQUENCE, PROTEIN, CELL, DEOXYRIBONUCLEIC

ACID (DNA).

White Blood Cells See LEUKOCYTES (white blood

cells).

White Corpuscles See LEUKOCYTES.

White Mold Disease The common name that refers to a plant disease caused under certain conditions (e.g., moist, humid, etc.) by the

Sclerotinia sclerotiorum fungus. In 1998, the U.S. Environmental Protection Agency (EPA) approved one herbicide (COBRAR, owned by Valent Corporation), whose active ingredient is the chemical lactofin, to be applied to soybean plants “at or near bloom stage” in order to trigger systemic acquired resistance (SAR, a sort of “immune response”) in those soybean plants against white mold disease. Use of No-tillage Crop Production (methodology) for some crops helps to reduce the incidence of white mold

disease. See also FUNGUS, SYSTEMIC ACQUIRED RESISTANCE (SAR), NO-TILLAGE CROP PRODUCTION, SOYBEAN PLANT.

Whole-Genome Shotgun Sequencing S e e

SHOTGUN SEQUENCING.

Wide Cross Refers to the plant breeding technologies/techniques utilized to cross two plant species that would not normally cross

in nature. See also TRADITIONAL BREEDING METHODS, TISSUE CULTURE, SPECIES.

Wide Spectrum See GRAM STAIN.

Wild Type The traditional/historical form of an organism as it is ordinarily encountered in nature, in contrast to domesticated strains, natural mutant, or laboratory mutant individuals (organisms). One example of a measurable difference between the two types is that wild strains of animals respond to the presence of EMF fields (e.g., weak magnetic fields such as those generated near power transmission cables), but laboratory strains of the same animals do not. See also STRAIN, MUTANT, PHENO-

TYPE, GENOTYPE, PSORALENE, SOLANINE.

Wobble The ability of the third base in a tRNA (transfer RNA) anticodon to hydrogen bond

with any of two or three bases at the 3′ end of a codon. This wobble (nonspecificity) allows a single tRNA species to recognize several different codons. See also TRANSFER

RNA (tRNA), CODON, BASE PAIR (bp), REDUNDANCY.

World Trade Organization (WTO) The international organization composed of the more than 100 nations that signed the General Agreement on Tariffs and Trade (GATT), which contained 38 Articles that lay out the rules and procedures which signatory countries must observe in their conduct of international trade and trade policy. GATT was WTO’s predecessor body. The WTO permits signatory countries to ban specific imports from other countries in order to protect the health of humans, animals, or plants. Such import bans are allowed based on the (GATT/WTO) Agreement on Sanitary and Phytosanitary Measures, or the Agreement on Technical Barriers to Trade; which were approved in 1994 by GATT.

WTO was established on January 1, 1995. The WTO’s Agreement on Sanitary and Phytosanitary (SPS) Measures requires that such import bans must be based on sound internationally agreed science. WTO recognizes only the following three international science organizations in order to resolve SPS disputes between member nations:

1.	Codex Alimentarius	Commission —
	for foods and food ingredients.
2.	International Plant Protection Conven-
	tion (IPPC) — for plants.
3.	International Office	of Epizootics
	(OIE) — for animal diseases.
See also SPS, CODEX ALIMENTARIUS COMMIS-
SION, INTERNATIONAL PLANT PROTECTION CON-
VENTION (IPPC), INTERNATIONAL OFFICE OF
EPIZOOTICS (OIE).
WP 900 See Z-DNA.
			W
WTO See WORLD TRADE ORGANIZATION (WTO).

© 2002 by CRC Press LLC

TERTIARY STRUCTURE,

X

X Chromosome A sex chromosome that usually occurs paired in each female cell, and single (i.e., unpaired) in each male cell in those species in which the male typically has two unlike sex chromosomes (e.g., humans).

See also CHROMOSOMES, IMPRINTING.

X-ray Crystallography The use of diffraction patterns produced by X-ray scattering from crystals (of a given material’s molecules) to determine the three-dimensional structure of the molecules. See also CONFIGURATION, CON-

FORMATION, PROTEIN

FOLDING.

Xanthine Oxidase An enzyme responsible for production of free radicals in the body. See

also HUMAN SUPEROXIDE DISMUTASE (hSOD).

Xanthophylls A “family” of carotenoids (i.e., plant-produced pigments that act as protective antioxidants in photosynthetic plants, and in the bodies of animals that consume those cartenoids). Among other plants, xanthophylls are produced by yellow carrots. Consumption of xanthophylls by humans and animals assists development of healthy eye tissue. Research indicates that consumption of xanthophylls by humans helps prevent lung cancer and some other cancers. See also CAROTENOIDS, ANTIOXI-

DANTS, OXIDATIVE STRESS, CANCER.

Xenobiotic Compounds Those compounds (e.g., veterinary drugs, agrochemical herbicides, etc.) designed for use in an ecosystem comprised of more than one species. For example, herbicides intended to kill weeds but leave commercial crops undamaged or veterinary drugs that are intended to kill parasitic worms but leave the host livestock unharmed.

Xenogeneic Organs From the Greek word xenos, stranger. Xenogeneic literally means “strange genes.” Refers to genetically engineered (e.g., “humanized”) organs that have been grown within an animal of another species. For example, several companies are working to engineer and grow — inside swine — a number of organs to be transplanted into humans that need those organs (e.g., due to loss of their own organs via disease or accident). If successful, this would free human organ transplant recipients from having to use immunosuppressive drugs continually in order to keep their body from “rejecting” the new organ. See also

IMMUNOSUPPRESSIVE, GRAFT-VERSUS-HOST DIS-

EASE (GVHD), CYCLOSPORIN, MAJOR HISTOCOM-

P A T I B I L I T Y C O M P L E X ( M H C ) , G E N E T I C

ENGINEERING.

Xenogenesis The (theoretical) production of offspring that are genetically different from, and genotypically unrelated to, either of the

parents. See also GENOTYPE, TRANSGENIC,

HEREDITY, GENETICS, MEIOSIS, GENETIC CODE.

Xenogenetic Organs See XENOGENEIC ORGANS.

Xenogenic Organs See XENOGENEIC ORGANS.

Xenograft See XENOTRANSPLANT.

Xenotransplant From the Greek word xenos, stranger. Xenotransplant is the implantation of an organ or limb from one species to another organism in a different species. When performed in animals, “rejection” of the transplant by the recipient’s immune system is a common response. See also GRAFT-

VERSUS-HOST DISEASE (GVHD), XENOGENEIC

ORGANS.

X

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GENETIC ENGINEERING,

Y

Y Chromosome A sex chromosome that is characteristic of male zygotes (and cells) in species in which the male typically has two unlike sex chromosomes. See also CHROMO-

SOMES.

YAC See YEAST ARTIFICIAL CHROMOSOMES (YAC).

Yeast A fungus of the family Saccharomycetaceae that is used by man especially in the making of alcoholic liquors and as a leavening agent in bread making. Some strains of yeast cells are also commonly used in bioprocesses, because they are relatively simple to genetically engineer (via recombinant DNA) and relatively easy to propagate (via fermentation) to yield desired products (e.g.,

proteins). See also FUNGUS, STRAIN, PREBIOTICS,

FERMENTATION, YEAST

ARTIFICIAL CHROMOSOMES (YAC), RECOMBINANT

DNA (rDNA).

Yeast Artificial Chromosomes (YAC) Pieces of DNA (usually human DNA) that have

been cloned (made) inside living yeast cells. While most bacterial vectors cannot carry DNA pieces that are larger than 50 base pairs, YACs can typically carry DNA pieces that are as large as several hundred base

pairs. See also YEAST, CHROMOSOMES, HUMAN

ARTIFICIAL CHROMOSOMES (HAC), BACTERIAL

ARTIFICIAL CHROMOSOMES (BAC), ARABIDOPSIS

THALIANA, DEOXYRIBONUCLEIC ACID (DNA),

CLONE (A MOLECULE), VECTOR, BASE PAIR (bp),

M E G A - Y E A S T A R T I F I C I A L C H R O M O S O M E S

(mega YAC).

Yeast Episomal Plasmid (YEP) A c l o n i n g vehicle used for introduction of constructions (i.e., genes and pieces of genetic material) into certain yeast strains at high copy number. YEP can replicate in both Escherichia coli and certain yeast strains. See also

PLASMID, CASSETTE, CLONE (AN ORGANISM),

GENE, GENETIC ENGINEERING, ESCHERICHIA COLIFORM (E. COLI), COPY NUMBER.

Y

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Z

Z-DNA A left-handed helix (molecular structure) of DNA, in contrast to A-DNA and B-DNA which are right-handed helix structures. The difference is in the direction of the double-helix twist. Z-DNA has the most base pairs per turn (in the helix), and so has the least twisted structure; it is very “skinny” and its name is taken from the zigzag path that the sugar-phosphate “backbone” follows along the helix. This is quite different from the smoothly curving path of the backbone of B-DNA. The Z-form of DNA has been found in polymers that have an alternating purine-pyrimidine sequence.

One possible biological importance of Z-DNA is that it is much more stable at lower salt concentrations, and there is a possibility that the Z-DNA form (of DNA within cells) is the cause of certain diseases (e.g., certain cancers). During 2000, Jonathan Chaires, Waldemar Priebe, and John Trent showed that WP 900 (i.e., the enantiomer of daunorubicin, a natural chemical compound which inhibits cancer) binds tightly (and selectively) to a Z-DNA polymer. See also

CELL, DEOXYRIBONUCLEIC ACID (DNA), B-DNA,

HELIX, DOUBLE HELIX, A-DNA, PURINE, BASE PAIR

(bp), PYRIMIDINE, ENANTIOMERS, CANCER.

Zearalenone One of the mycotoxins (i.e., toxins produced by a fungus), it causes reproductive difficulties in swine (e.g., reduced sperm production, halting of estrus, etc.) when consumed by animals (e.g., in contaminated grain such as corn/maize). Zearalenone is produced by certain strains of Fusarium fungi when climate (moisture and temperature) conditions during the grain growing season, combined with entry points (e.g., holes chewed into the grain plants by insects) facilitate growth of those Fusarium

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©2001 by CRC Press LLC

©2002 by CRC Press LLC

strains in grain. See also TOXIN, MYCOTOXINS,

FUNGUS, STRAIN, FUSARIUM, LACTONASE.

Zeaxanthin A carotenoid (i.e., “light harvesting” compound utilized in photosynthesis) that is naturally produced in Brussels sprouts, summer squash, maize, avocado, green beans, and dark green leafy vegetables. Zeaxanthin is a phytochemical/nutraceutical whose consumption by humans has been shown to reduce risk of the disease age-related macular degeneration, a leading cause of blindness in elderly people. See also CAROTENOIDS, PHOTO-

SYNTHESIS, PHYTOCHEMICALS, NUTRACEUTICALS.

Zinc Finger Proteins Protein molecules bearing at least one “finger shaped” molecular appurtenance which acts to either repress or activate transcription (i.e., of the gene the “finger” touches within a DNA molecule). Thus, they could potentially be utilized in functional genomics (i.e., to study the specific function of a given gene). See also

FUNCTIONAL GENOMICS, PROTEIN, GENE, TRANSCRIPTION, REPRESSION (of gene transcription), PRO-

MOTER, DEOXYRIBONUCLEIC ACID (DNA).

ZKBS (Central Committee on Biological Safety) The advisory body on safety in gene-splicing labs and plants for the German Government’s Ministry of Health. It is the German counterpart of the American government’s Recombinant DNA Advisory Committee (RAC), Australia’s Genetic M a n i p u l a t i o n A d v i s o r y C o m m i t t e e (GMAC), Brazil’s National Biosafety Commission (CTNBio), and the Kenya Biosafety Council. The ZKBS is composed of 10 experts from the biology and ecology sectors, trade union representatives, and representatives from the industrial sector and environmental pressure groups. The ZKBS advises the Ministry of Health and the individual

Z