Page 104 - JRT Magazine - 2023 Issue 2
P. 104
Education
Incomplete nose pigmentation
Puppies are usually born with pink noses. The
pink is not a pigment; it’s a lack of pigment. The
pigment, eumelanin, in the nose develops over the
next 2 to 12 weeks. In a few cases, it doesn’t finish
until 3 to 4 months of age, and rarely, parts of the
nose may remain unpigmented in adulthood.
Merle
The gene causing the merle coat pattern
is the same in every dog breed. It is an
ancient gene. It only takes one M allele
to produce the splotching. JRTs/Russell
Somatic mutation Terriers should be mm since merle is not
Somatic mutation occurs during the development an acceptable coloring for the JRT/Russell
of the embryo. It is a mutation of part of the Terrier. The merle pattern is associated
pigment, allowing patches of another color with several health issues. Even a single
to appear on the dog. It can occur if a single copy of M raises the risk of hearing loss.
cell mutates early on in development. All cells Homozygous merles (MM) are usually
descending from that single mutated pigment blind and deaf. Merle is complicated in
cell will then be a different color as the embryo its genetic expression and the discussion
grows. It is not hereditary because it is a localized of merle goes beyond the scope of this
mutation. These localized patches have a different article. Suffice it to say that genetic color
genotype to the rest of the dog. The condition is testing should be used to remove Mm
sometimes known as mosaicism. (Not the same JRTs from the breeding population.
as a chimera).
104 | A Worldwide Magazine for the Jack Russell Terrier / Russell Terrier • Issue 2/2023
