Allele: An alternative form of a gene. A gene may
have several alleles (be multi-allelic) but a dog can only
have two alleles of any gene and these may be identical or
Dominant: Relates to an allele of a gene which, when
present in a single dose, will mask the presence of another.
Usually depicted by upper case letters.
Gene: The unit of inheritance.
Genotype: The genetic structure of the animal. What
an animal carries in its genetic makeup but which may not be
apparent in his appearance.
Heterozygous: Strictly different -- used to indicate
dogs that carry different alleles of a gene at a specific
locus. Thus Aa and Bb are examples of heterozygous
Homozygous: Strictly the same -- used to indicate
dogs carrying the same allele of a gene in duplicate. Thus
AA and aa are homozygous animals.
Locus (plural loci): A particular point on a
specific chromosome. Any gene is always found at the same
Phenotype: The visible expression of a character.
Thus BB and Bb would be different genotypes, but the same
Recessive: Refers to an allele that needs to be
present in duplicate in order to indicate its presence. In a
single dose it will be masked by a dominant allele.
"Genetics of the Dog", by Malcom B. Willis. Howell
Book House, New York. 1989.
"The Inheritance of Coat Color in Dogs", by
Clarence C. Little. Howell Book House, New York. 1957.