Molecular Sciences Bldg
21, James Cook University,
Telephone: 61-7-4781 6265
Fax: 61-7-4781 6078
|COAT COLOUR IN LABRADORS
Only three coat colours are recognised in
labradors: black, chocolate and yellow. Although slight variations in
shading are conferred by a number of genes, distinction between these
main colour groups are encoded by only two loci.
One of two alleles
can be expressed at the E locus: E (big E) and e
E). A single copy of the E allele prevents the expression of a
coat colour. Dogs that express one or two copies of the E
at the E locus are black or brown; the E allele is dominant.
Dogs that express two copies of the e allele at the E
are yellow; the e allele is recessive.
One of two alleles can be expressed at the B
locus: B (big B) and b (little B). Providing a dog is
e at the E locus, dogs that express one or two copies of
allele at the B locus are black; the B allele is
Providing a dog is not homozygous e at the E locus,
that express two copies of the b allele at the B locus
chocolate; the b allele is recessive.
The following table illustrates the
possible combinations of alleles associated with each of the three coat
colour phenotypes observed
What parental genotypes could produce a litter containing pups of all
three coat colours?
A NOTE ON NOMENCLATURE:
Gene names are italicised in order to distinguish
them from any protein products that they may encode - the names of
are not italicised. Capitalisation of the first letter of an allele
is conventionally used to denote the dominant allele; lower case to
a recessive allele.The allele expressed at a particular locus is
by following the gene name with the superscripted allele name (e.g. Ee).
Heterozygosity can be indicated with a forward slash (/) between the
allele names (e.g. EE/e). Where a single functional
dominates, it may be described as the "wild type" allele and be
with a plus symbol (+). Homozygosity for the wild type allele may
be indicated by +/+.
COAT COLOUR GENETICS LINKS:
OTHER GENETICS LINKS:
Comparative Genomics Centre,
Cook University, Key words: Autoimmune diabetes, Type 1 diabetes
childhood diabetes, lupus, systemic lupus erythematosus, haemolytic
hemolytic anemia, Coombs' test, antinuclear antibodies, renal failure,
glomerulonephritis, gastritis, type A gastritis, pernicious anemia.