Page 75 - Aussie Magazine - 2023 Issue 2

that there is a lack of melanin pigment in one eye. probably are either more than one gene involved
Heterochromia can affect the entire iris or just part or there is regulatory DNA that influences the
of it. If the eye is partially affected, it may look like function of the gene(s) that cause this type of
the eye is marbled or speckled. blue eye. Blue-eyed non-merle Aussies are not
prone to congenital deafness. They are sound
The merle gene works by causing a variation in and are correct as per the breed standards.
pigment in the hair and skin cells. This creates
the mottled pattern that merle dogs are so Paw Print Genetics has done a small study of
well known for. It’s technically a dilution gene Blue-Eyed Tris (BET) to determine whether
meaning that it lightens the intensity of other variations of the merle gene might play a role
pigments. It simply does it in an uneven pattern. in their appearance. 38 dogs were included in
About merle you can find out more in another the study. Owners had submitted photographs
article in this magazine – Merle series. of their dogs to demonstrate their BET status.
60.5% were non-merle (m/m) and 14 (36.8%)
Sometimes Australian Shepherds which are not had a single copy of a cryptic version of merle.
merle will have blue eyes. Either or both eyes The remaining dog was double cryptic. This study
may be blue. Sometimes they are half blue/half was too small to be conclusive but the significant
pigmented. They are rarely flecked or marbled. proportion of BET dogs who had at least one copy
This kind of blue eye has nothing to do with the of a cryptic version of merle indicates this gene
merle gene, white trim genes or the albino gene variant may in some cases contribute to blue eyes.
(which probably does not exist in dogs). These However, the majority of the dogs who had two
eyes are completely sound, though perhaps wild type copies of merle indicate that there are
slightly light sensitive just as blue-eyed people other factors that contribute to blue eyes. There
are slightly more light-sensitive than those with are a number of breeds of dog which do not
brown eyes. Siberian Huskies are an example of have merle but sometimes have blue eyes. It is
another breed with this type of blue eye. probable that some BET Aussies may have some
other gene which gives them blue eyes.
The mode of inheritance is unknown, but since
the blue eyes can be single or a pair and an We don’t know exact answer and what is Behind
individual eye may be half-and-half, there Blue Eyes. Maybe it's a mystery.....

A Worldwide Magazine for the Aussie • Issue 2/2023 | 75