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gallery forest: A stretch
of forest along a river or stream.
gamete: Mature reproductive
cells that are specialized for sexual fusion. Each gamete is haploid
and fuses with a cell of similar origin but of opposite sex to producea
diploid zygote.
gametogenesis: The
formation of male and female gametes by meiosis.
gametophyte: The haploid
sexual generation in the life cycle of plants that produces the
gametes.
gathering: Food acquisition
with postponed consumption.
GC box: A eukaryotic
promoter element with the consensus sequence 5'-GGGCGGG-3' that
can be found in either orientation upstream of the transcription
initiation site. The GC boxes appear to help the RNA polymerase
near the transcription start point.
gene (Medelian factor):
A unit of inheritence carried on a chromosome, transmitted from
generation to generation by the gametes and controlling some aspects
of the development of an individual.
genealogical species:
Species that are defined by common ancestry and are treated as distinct
individuals with definite beginnings and ends.
gene flow: A form of
genic exchange in which genetic material is transferred between
populations because of interbreeding or mate exchange between them.
gene frequency: The
percentage or proportion of a given allele in a sample.
gene locus: See locus.
gene marker: See genetic
marker.
gene mutation: A heritable
alteration of the genetic material, usually from one allelic form
to another.
gene pool: The total
genetic information encoded in the total genes in a breeding population
existing at a given time.
generalized: (1) Primitive
or plesiomorphic, similar to the ancestral condition; (2) adapted
to a broad range of resources.
generalized transduction:
A type of transduction in which any gene may be transferred between
bacteria.
gene redundancy: A
situation in which tRNA genes occur two or more times in the E.
coli chromosome.
gene regulatory elements:
Base-pair sequences associated with a gene, which are involved in
the regulation of gene expression.
gene segregation: See
principle of segregation (first law).
genetic code: The base-pair
information that specifies the amino acid sequence of a polypeptide.
genetic correlation
(pleiotropy): Covariation of features in populations because they
share some genes. An association between the genes that determine
two traits.
genetic counseling:
The procedures whereby the risks of prospective parents having a
child who expresses a genetic disease are evaluated and explained
to them. The genetic counselor typically makes predictions about
the probabilities of particular traits (deleterious or not) occurring
among children of a couple.
genetic drift: A mechanism
for evolutionary change caused by the random fluctuations of gene
frequencies from one generation to the next, or from any form of
random sampling from a gene pool. Any change in gene frequency due
to chance in a population.
genetic engineering:
The alteration of the genetic constitution of cells or individuals
by directed and selective modification, insertion, or deletion of
an individual gene or genes. In some cases, novel gene combinations
are made by joining DNA fragments from different organisms.
genetic map (linkage
map): A representation of the genetic distance separating nonallelic
gene loci in a linkage structure.
genetic mapping: The
uses of genetic crosses to locate genes in chromosomes relative
to one another.
genetic marker (gene
marker): Any genetically controlled phenotypic difference used in
genetic analysis, particularly in the detection of genetic recombination
events.
genetic recombination:
A process by which parents with different genetic characters give
rise to progeny so that genes in which the parents differed are
associated in new combinations. For example, from A B to a b the
recombinants A b and a B are produced.
genetic reorganization:
The dislinking of co-adapted alleles (alleles with interdependent
frequencies) due to random fluctuations because of small population
effects during peripatric speciation, followed by the establishment
of new co-adapted allele systems.
genetics: The science
of heredity that involves the structure and function of genes and
the way genes are passed from one generation to the next.
genetic variance (VG):
Genetic sources of phenotypic variation among individuals of a population;
includes dominance genetic variance, additive genetic variance,
and epistatic genetic variance.
genic exchange: The
sharing of genetic material because of gene flow or migration.
genioglossal pit: The
notch on the inside border of the mandibular symphysis marking the
origin of the genioglossus (tongue) muscle.
genome: The entire
DNA component of a cell, a structured array consisting of genes
and their parts, units of DNA replication, and nonfunctioning regions.
genomic imprinting:
Phenomenon in which the expression of certain genes is determined
by whether the gene is inherited from the female or male parent.
genomic library: The
collection of molecular clones that contain at least one copy of
every DNA sequence in the genome.
genotype: The genetic
make-up of an organism, its total genetic material.
genotypic frequencies:
The frequencies or percentages of different genotypes found within
a population.
genotypic sex determination:
The process by which the sex chromosomes play a decisive role in
the inheritance and determination of sex.
genus (genera): A group
of closely related species, a monophyletic category for the taxon
above the species level that includes one or more species.
geochemical analysis:
The investigatory technique which involves taking soil samples at
regular intervals from the surface of a site, and measuring their
phosphate content and other chemical properties.
geomagnetic reversal:
An aspect of archaeomagnetism relevant to the dating of the Lower
Paleolithic, involving complete reversals in the earth's magnetic
field.
geomorphology: A subdiscipline
of geography, concerned with the study of the form and development
of the landscape, it includes such specializations as sedimentology.
germ-line mutations:
Mutations in the germ-line of sexually reproducing organisms may
be transmitted by the gametes to the next generation, giving rise
to an individual with the mutant state in both its somatic and germ-line
cells.
gestation: The period
from fertilization to birth.
glabella: A place on
the midline of the frontal bone between the browridges, superciliary
arches, or upper orbital borders.
glaciation: Ice age,
the temporary enlargement of continental ad momentum glaciers associated
with worldwide climate changes.
glenoid fossa: (1)
The mandibular fossa; (2) or the glenoid fossa of the gleno-humeral
joint.
glenoid joint: (1)
The temporo-mandibular articulation; (2) the socket part of the
shoulder ball-and-socket joint on the scapula.
glottochronology: A
controversial method of assessing the temporal divergence of two
languages based on changes of vocabulary (lexicostatistics), and
expressed as an arithmetic formula.
glucose effect: See
catabolite repression.
gluteus maximus: Large
muscle extending from the lateral and rear surface of the ilium
to the gluteal tuberosity of the femur, causing extension and rotation
at the top.
gluteus medius: Muscle
extending from the lateral surface of the ilium to the greater trochanter
of the femur, causing abduction at the hip.
gluteus minimus: Large
muscle extending from the lateral surface of the ilium to the greater
trochanter of the femur, causing abduction and rotation at the hip.
Goldberg-Hogness box
(TATA box, TATA element): Found approximately at position-30 from
the transcription initiation site. The Goldberg-Hogness sequence
is considered to be the likely eukaryotic promotor sequence. The
consensus sequence for the Goldberg-Hogness box is TATAAAAA.
gonial angle: The smoothly
curced area where the back of the ramus meets the bottom of the
corpus.
gracile: Slender, delicately
built, weak muscle attachments or bony butresses. A relative condition
referenced to another condition.
grade: A grouping characterized
by a general level of organization (or sharing a suite of features).
Grades composed of independent lineages that may or may not be monophyletic.
gradualism: A theory
that evolution progresses by the extension of microevolutionary
processes over long periods of time, the gradual modification of
populations. The concept does not imply continuous evolution, or
evolution at a constant rate.
graminivore: An animal
that eats primarily grains; often used to describe seed-eating.
great apes: The four
large living apes: bonobos, chimpanzees, gorillas, and orangutans.
Great apes are not a monophyletic group.
greater sciatic notch:
U-shaped notch at the back of the innominate characteristics of
bipedal hominid pelves caused by the rearward and inferior displacement
of the sacrum relative to the ape anatomy.
greater trochanter:
Very large process on the lateral and proximal end of the femur
shaft, for the attachment of muscles that stabilize the hip during
one-legged balance (whether in standing or in bipedal locomotion).
gregarious: Social
orientation to behavior, living in regular social groups.
grind: In chewing,
the action resulting from applied forces with components that are
both perpendicular and parallel to the plane of contact between
the teeth.
grooming: Cleaning
the body surface by licking, biting, picking with fingers or claws,
or other kinds of manipulation.
group I-intron self-splicing:
See self-splicing.
group selection: Evolutionary
process involving differential survival and reproduction of competing
groups.
guanine (G): Purine
base found in RNA and DNA. In double-stranded DNA, guanine pairs
with the pyrimidine cytosine.
gummivore: An animal
specializing in gums, saps, and other tree exudates.
gyrus: The "hill"
of the convolutions on the surface of the brain caused by the folding
of the cortex.
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