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Alpaca Genetics
Glossary of Alpaca Terms
GAMETE:
A sex cell; a sperm or egg.
GAMETE SELECTION:
The process that determines which egg matures and which sperm succeeds in
fertilizing the egg.
GENE:
The basic physical unit of heredity consisting of a DNA sequence at a specific
location on a chromosome.
GENE FREQUENCY:
Also allelic frequency. The relative frequency of a particular allele in a
population.
GENE LINKAGE:
The occurrence of two or more loci of interest on the same chromosome.
GENE MAP:
Also a linkage map or chromosome map. A diagram showing the chromosomal
locations of specific genetic markers and genes of interest.
GENERATION INTERVAL:
(1) The amount of time required to replace one generation with the next. (2) In
a closed population, the average age of parents when their selected offspring
are born.
GENETIC CORRELATION:
(1) A measure of the strength (consistency, reliability) of the relationship
between breeding values for one trait and breeding values for another trait.
(2) A measure of pleiotropy (the production of change in more than one trait).
GENETIC MARKER:
A detectable gene or DNA fragment used to identify alleles at a linked locus.
GENETIC MERIT:
The accumulative positive genotype of an individual animal or herd which can be
passed onto progeny.
GENETIC PREDICTION:
The area of academic animal breeding concerned with measurement of data,
statistical procedures, and computational techniques for predicting breeding
values and related values.
GENETIC TREND:
Change in the mean breeding value of a population over time.
GENETIC VARIATION:
In the context of the key equation for genetic change, variability of breeding
values within a population for a trait under selection.
GENOTYPE:
(1) The genetic makeup of an individual. (2) The combination of genes at a
single locus or at a number of loci. Geneticists speak of one-locus genotypes,
two-locus genotypes, and so on.
GENOTYPIC VALUE:
The effect of an individual's genes (singly and in combination) on its
performance for a trait.
GERM CELL:
A sex cell; a sperm or egg; a gamete.
GERM PLASMA:
Genetic material in the form of live animals, semen, or embryos.
GRADING-UP:
Also topcrossing. (1) A mating system designed to create a purebred population
by mating successive generations of non-purebred females to purebred sires. (2)
A mating system designed to convert a population from one breed to another by
mating successive generations of females descended from the first breed to
sires of the second breed.
GREASY ALPACA FLEECE:
A commercial term identifying unwashed alpaca fleece.
GUANACO:
A wild member of the New World camelidae family, Lama gunaimicoe.
GUARD HAIR:
Also kemp. Coarse medulated fiber. A second coat of fiber found in llamas,
vicuna, guanacos, and, to a lesser degree, alpacas.
HACIENDA:
A large land holding that originated with the land grant system used by Spanish
conquistadores. In size, comparable to an American plantation.
HALF SIBS:
Half brothers and sisters.
HEMBRA:
Female alpaca or animal.
HERITABILITY:
A measure of the strength of the relationship between performance (phenotypic
values) and breeding values for a trait in a population. Heritability in the
broad sense.
HOMOLOGUE:
One of a pair of chromosomes having corresponding loci.
HETEROZYGOUS:
A one-locus genotype containing different alleles which express themselves in
different ways.
HISTOGRAM:
(1) The most common graphical presentation of quantitative data. The variable
of interest, such as fiber diameter measured in microns, is placed on the
horizontal axis and the frequency values, such as the percentage of fibers per
micron, are placed on the vertical axis. (2) A micron test report that includes
administrative information provided by the identification sent in with the
individual sample. The histogram on such a report depicts the measurement of
2000 fibers in scale.
HOMOZYGOUS:
A one-locus genotype containing identical alleles which express themselves in
identical fashion.
HUACAYA:
A breed of alpaca characterized by a well-crimped fleece that grows
perpendicular to the skin.
HUARIZO:
A crossbred animal. A term most often used to describe a llama-alpaca cross.
Characterized by weak, medulated fiber and poor breed type.
HYBRID:
An individual that is a combination of species, breeds within species, or lines
within breeds.
HYBRID VIGOR:
An increase in the performance of hybrids over that of purebreds, most
noticeably in traits such as fertility and survivability.
IDENTICAL BY DESCENT:
Two genes that are copies of a single ancestral gene.
INBREEDING:
The mating of relatives.
INBREEDING CO-EFFICIENT:
The measure of the level of inbreeding in an individual determined by (1) the
probability that both genes of a pair in an individual are identical by
descent, or (2) the probable proportion of an individual's loci containing
genes that are identical by descent.
INBREEDING DEPRESSION:
The reverse of hybrid vigor. A decrease in the performance of inbreds, most
noticeably in traits such as fertility and survivability.
INDEPENDENT ASSORTMENT:
The independent segregation of genes at different loci during gamete formation.
INDEPENDENT CULLING LEVELS:
Minimum standards for traits undergoing multiple trait selection. Animals
failing to meet any one standard are rejected regardless of merit in other
traits.
INDEPENDENT GENE EFFECT:
The effect of a gene independent of the effect of the other gene at the same
locus (dominance) and the effects of genes at other loci (epistasis).
INDICATOR TRAIT:
A trait that may or may not be important in itself, but is selected for as a
way of improving some other genetically correlated trait.
INDIRECT SELECTION:
Selection for one trait as a means of improving a genetically correlated trait.
KEMP:
Guard hair or medulated fiber.
LAMA:
Scientific name for the genus containing llamas, alpacas, guanacos, and
vicunas; vicunas are sometimes separated into their own genus.
LINE:
A group of related animals within a breed.
LINEBREEDING:
The mating of individuals within a particular line. A mating system designed to
maintain a substantial degree of relationship to a highly regarded ancestor or
group of ancestors without causing high levels of inbreeding.
LINECROSSING:
The mating of sires of one line or line combination to dams of another line or
line combination.
LINKAGE:
The occurrence of two or more loci of interest on the same chromosome.
LINKAGE ANALYSIS:
A mathematical procedure that uses information from pedigreed populations to
determine whether two loci are linked and, if so, how closely.
LOCUS/LOCI:
The specific location of a gene on a chromosome.