Page 100 - JRT Magazine - 2023 Issue 2

Education
T locus named for Ticking, which affects
the white areas created by piebald spotting Sp.
With ticking, small spots color, matching the
dog’s base color can be seen. If a dog is black
and tan, ticking of both colors may be seen
exactly in the same zones of the base coloring.
Ticking matches the dog’s base color.
Locus T includes three alleles, but just
two of them are relevant for Jack Russell
Terriers: dominant T codes for the presence
of ticking and recessive t codes for the
absence ticking. The possible genetic
formulas for this locus in JRTs are:
• TT – homozygous for ticking. This dog
carries two copies of allele T and has
ticking on white areas. The progeny
will have ticking as well.
• Tt – heterozygous for ticking. This dog
carries one copy of allele T responsible
100 | A Worldwide Magazine for the Jack Russell Terrier / Russell Terrier • Issue 2/2023
for the presence of ticking and one copy
of allele t responsible for its absence.
This dog will show ticking itself, but it
potentially can have progeny without
it, depending on the genotype of the
partner.
• tt – homozygous for absence of ticking.
This is a dog without ticking, but it can
have progeny with or without ticking,
depending on the genotype of the
partner.
The density and amount of ticking varies
a lot from dog to dog and for the moment
there is no clear explication as to why. It
is possible that homozygous TT animals
have heavier ticking than heterozygous Tt.
Ticking appears with the ageing of the
dog. All JRT puppies are born with clear
white-spotting patches over their true
colors, which makes the dog appear as
though it is white with colored patches.
Tiny spots of color (ticking) are not evident
at birth. Ticking is not seen until at least 1
to 2 months of age, and some dogs do not
show the first tickings until much older.
At 4 to 8 weeks of age, ticking may start to appear on the
muzzle.