GASee gibberellins.

gametocide An agent used to selectively kill either male or female gametes.

gap A missing section on one of the strands of a DNA duplex. The DNA will therefore have a single-stranded region.

gel The inert matrix used for the electrophoretic separation of nucleic acids or proteins. See also electrophoresis; polyacrylamide gel electrophoresis; sequencing gel.

gel filtration A type of fractionation procedure in which molecules are separated from each other according to differences in size and shape; the action is similar to that of molecular sieves. Dextran gels (three-dimensional networks of polysaccharide chains) are usually used in this method.

gene Part II.

gene bank The collection of cloned DNA fragments that, ideally, represent all the sequences of a single genome. Synonyms: gene library; genomic library; library.

gene mapping Determination of the relative locations of genes on a chromosome or within a genome.

gene sequencing Determination of the identity and order of nucleotide bases in a strand of DNA.

generation Symbols for generations include BC (backcross), F (filial, or hybrid), M (mutant), R (regenerant), S (selfed), and Syn (synthetic). The generation number is usually indicated by a subscript: F₂, R₀, S₁, etc., but Syn 2. Compare C for cycle of selection (not necessarily a generation; no subscript).

genetic correlation Correlation between the genotypic values of two characters, or of two individuals with respect to the genetic character or different characters.

genetic engineering The use of in vitro techniques to produce DNA molecules containing novel combinations of genes or other sequences in living cells that make them capable of producing new substances or performing new functions. Usage: A popular term for such technologies as a whole.

genetic shift A change in the germplasm balance of a cross-pollinated variety, usually caused by environmental selection pressures.

genome Part II.

genomic librarySee gene bank.

geographic range Geographic limits of the ecologic range; geographic extent of actual occurrences of a species.

germination (1) Resumption of active growth by the seed embryo, culminating in the development of a young plant. (2) In seed laboratory practice: emergence and development from the seed embryo of those essential structures, which, for the kind of seed in question, are indicative of the ability to produce a normal plant under favorable conditions.

gibberellic acid One of the gibberellins. Abbr.: GA₃.

gibberellins Part II.

ginned lint Cotton fibers after they have been removed from the seed.

glutenin The dilute alkali-soluble fraction of proteins in wheat.

Goldberg-Hogness boxSee TATA box.

grade, cotton A system of scales used in classifying cotton with regard to color, trash content, and preparation.

grain grade Market standard established to describe the amount of contamination, grain damage, immaturity, test weight, and marketable traits.

grain, percent Threshed grain weight x 100/(threshed grain weight + stalk weight).

grain-to-stalk ratio Threshed grain weight/stalk weight.

grass Member of the plant family Poaceae.

grassland (1) Land on which the vegetation is dominated by grasses. Compare pastureland; rangeland. (2) More generally, any plant community in which grasses and/or legumes make up the dominant vegetation.

grazable forestland Forestland that produces, at least periodically, sufficient understory vegetation that can be grazed. Forage is indigenous or, if introduced, is managed as though it were indigenous. Synonyms: grazable woodland; woodland range; forest range.

grazer (1) Animal that grazes in situ grass as herbage. (2) On experimental pastures, animals that may or may not remain on specified pasture treatment for the entire grazing period or season but are of a kind or physiological condition not necessarily represented on all pasture treatments for the entire grazing period or season. See also tester animals.

grazing capacitySee carrying capacity.

grazing event The length of time that an animal grazes without stopping. Compare grazing period.

grazing land management The manipulation of the soil-plant-animal complex of the grazing land in pursuit of a desired result. Usage: For more specific applications, substitute the appropriate term (e.g., grassland) for grazing land.

grazing management unit The grazing land area used to support a group of grazing animals for a grazing season. It may be a single area, or it may have a number of subdivisions. See also paddock; pasture.

grazing period The length of time that grazing livestock or wildlife occupy a specific land area. Compare grazing event.

grazing pressure The relationship between the number of animal units or forage intake units and the weight of forage dry matter per unit area at a given time; an animal-to-forage relationship. The inverse of forage allowance.

grazing system A defined, integrated combination of animal, plant, soil, and other environmental components and the grazing method or methods by which the system is managed to achieve specific results or goals. Usage: Descriptive common names may be used; however, the first usage of a grazing system name in a publication should be followed by a description using a standard format. This format should include at least the following information: number, size, kind, slope, erosion status, and soil classification of land units; number, kind, sex, size, and age of livestock; duration of use and nonuse periods for each unit in the system; grazing methods; types of forage; geographic location and elevation; and type of climate and mean annual and seasonal temperatures and precipitation.

groat The caryopsis or kernel of oat after the husk has been removed.

gross energy The amount of heat that is released when a substance is completely oxidized in a bomb calorimeter containing oxygen at 25 to 30 atmospheres pressure (~2.5-3.0 MPa).

growth analysis Mathematical analysis of crop or plant growth (following original concepts of Blackman and of West, Briggs, and Kidd) using relative growth rate (RGR), net assimilation rate (NAR), leaf area growth rate (LAR), and crop growth rate (CGR). Generally involves the relationship of these variables to other crop or environmental variables as integrated over time (sampling interval). See also assimilation; growth rate.

growth rate A rate of change in growth (e.g., in number size or mass) of an organ, organism or community. (1) Absolute growth rate is represented by dx/dt as change in amount per unit time. (2) Specific (or relative) growth rate is dx/xdt, change per unit amount per unit time (with units of 1/time). (3) Crop growth rate is a specific plant growth analysis term denoting the absolute growth rate of mass per unit land, A, thus dw/Adt, usually in units of grams per meter per day (g m^-1 d^-1). Usage: Relative growth rate (RGR) is the usual term in plant growth analysis, whereas specific growth rate (() is used in most other disciplines.

growth regulatorSee hormone.

growth stageSee developmental stage.

guanineSee G.

guide sequence An RNA molecule (or a part of one) that hybridizes to eukaryotic mRNA and aids in the splicing of intron sequences from a primary transcript. Guide sequences may be either external or internal to the mRNA being processed and may hybridize either to the intron or exon sequences close to the splice junction.