. . Alleles: different
versions of the same gene (found at the same locus but in homologous chromosomes or in
different individuals) that may produce different phenotypes. . Allele frequency: the fraction
of all the alleles of a gene in a population that are of one type. . Assortative mating: a mating
scheme that relies on the pairing of unrelated individuals with similar phenotypes
to obtain consistency of type and reinforce desirable traits. . Back to top . Codominant alleles:
two alleles that have different effects that are distinguishable in a heterozygous
individual (e.g. AB blood groups) . Cross-breeding: crossing two
different breeds. . Back to top . Dominant allele:
one that determines the phenotype even when there is only one copy (i.e. in a heterozygous
individual). . Drift: changes in allele frequencies
over time due to chance (as opposed to selection or mutation). . Back to top . Effective population
size (Ne): the size of a hypothetical stable, randomly-mating population that
would have the same rate of gene loss or increase in inbreeding
as the real population (size N). As all finite populations are inbred
to some degree and generally do not choose mates at random, Ne is
typically 1/10 N or less, particularly if fewer males
breed than females. . Epistasis: used to describe
the situation where one gene's expression prevents the expression of another
(e.g. you cannot determine whether an albino would have
had black or brown hair, though these two traits are controlled
by separate genes.) . Back to top . Fitness (relative):
The reproductive success of individuals of a particular genotype relative
to the most fit genotype. . Fixation: loss of all alleles
of a gene but one. . Founder: an individual drawn
from a source population who contributes genetically to the
derived subpopulation. . Founder effect: changes in allele
frequencies that occur when a subpopulation is formed from
a larger one. Typically many rare and usually undesirable alleles
are excluded while a few carried by the founders get a big boost
in frequency. . Founder equivalents: the number
of hypothetical founders that would have the same diversity
as the descendant population. Generally much smaller than
the actual number due to unequal use and allele loss (gene dropping). . Back to top . Gene: that portion
of the genome that carries the information for a single protein. (In cases
of proteins with multiple subunits, there may be a gene for each.) . Gene dropping: loss of alleles
due to genetic drift. . Genetic bottleneck: when population
numbers are temporarily reduced to a level insufficient
to maintain the diversity in the population. . Genetic diversity: usually expressed
in terms of percentage of genes that are polymorphic and/or
are heterozygous. . Genome: (Genome:All the
genetic material in the chromosomes of an INDIVIDUAL; its size is generally
given as its total number of base pairs) which is sometimes misconstrued
as "gene pool" (Gene pool: All the variations of genes in a BREED
or species). . Back to top . Heritable: passed
on from parents to progeny through the chromosomes/DNA. . Heritability: the fraction of
the variability in a trait that is caused by genetic differences. . Heterozygous: carrying two different
alleles of a gene. . Heterozygous advantage: a situation
where the heterozygous genotype for a particular gene
shows the highest relative fitness. . Heterozygous insufficiency:
when the heterozyous genotype lacks sufficient gene product to have
the normal phenotype. (Approximately equivalent to
partial dominance.) . Heterosis: a situation where
crossing two inbred lines yields progeny that are more healthy/vigorous
than their parents. (More commonly used in plant
breeding.) . Homologous chromosomes: in higher
plants and animals, chromosomes are found in nearly
identical "homologous" pairs, one coming from the sire
and the other from the dam. A dog has 39 pairs, or 78 in
total. Only one of each, chosen at random, is passed on through
eggs or sperm to the progeny. . Back to top . Linebreeding:
a scheme that attempts to maintain a high contribution of one or two ancestors
through successive generations. Often used by breeders
for any inbreeding less intensive than between first-degree
relatives. . Linkage: a measure of how frequently
two genes found on the same chromosome remain together
during gamete (egg or sperm) formation. . Locus: the location of a gene
on a chromosome. . Back to top . Map (aka linage
map): a drawing showing the location of and relative distances between
genes on a chromosome. . Mean kinship (mk): a measure
of how related an individual is to the other members of a population.
Generally computed as the average IC for the hypothetical
progeny of the individual mated to all other members of
the population (both sexes). A low average mk for a population
indicates that most of the diversity carried by the
founders has been retained. . Monomorphic genes: have only
one common allele (rare alleles with frequencies of less than
0.001% may still occur). . Mutation: a change in the sequence
of the base pairs in a DNA molecule. . Mutation rate: the number of
new mutations that occur per gene per gamete per generation. . Back to top . Outcrossing:
mating two individuals of the same breed that are sufficiently unrelated that
the IC of the progeny is lower than the average of the parents. . Back to top . Polymorphic
genes: have 2 or more common alleles in the population. . Back to top . Recombination:
the reciprocal exchange of portions of two homologous chromosomes (usually
equivalent) during gamete formation. . Recombinant frequency (RF):
how often two linked genes are separated by recombination,
generally expressed as a percentage of total progeny. . Back to top . . .