My Apologies

I have not been posting to this blog as much as I should, but with my job, it's hard to maintain two blogs, two websites, keep up to date with my friends, train my dog, do homework and further pursue my photography.  So, my apologies, and I promise to make a post over winter break!

Merle: Heterozygous and Homozygous

To start off, Merle is not a color, it is a pattern that affects the base color of a dog.  The solid base color has a splotched appearance on top of a lighter color (ex.black on top of light grey).  There are also sometimes possible lighter patches of the base color splotched in the merle.

In this photo, you can see the mix of darker spots on top of the lighter color.  Also, you can see the Black (original base color) with a "Blue" color spot on top of it.  This shows the color spots can vary on a merled dog.  This can also occur on Red Merle dogs, but it does seem to occur more readily.

This dog is tricolor along with a Red Merle.  There are at least two shades of red in this merle pattern.

The above dogs are heterozygous males, which means they are Mm.  A homozygous merle is MM.  I will now present examples of Double Merle dogs.

A double merle dog occurs when two heterozygous merle dogs are bred together.

The above chart shows what happens when two Heterozygous merle dogs are bred.  25% of the offspring should be Homozygous merle, 50% regular merle, and 25% will not be merle at all, even though both parents are merle.

Another name for a homozygous merle is a Double Merle, Double Dilute or Lethal White.  The issues in Double Merles can be very serious.  The dogs can turn out to be blind and/ or deaf.  But blindness is not the only effect on the eyes, there are many defects that can occur.  Starburst pupils, dropped pupils and  micropthalmic or micropthalmia are a few of the other issues.  

Starburst Pupils - when the pupil has spiky projections

Eccentric Pupils - when the pupil has jagged or irregular edges

Coloboma - makes the eye very light sensitive because the pupil doesn't react as well as it should

Subluxated Pupil (Dropped Pupil) - the pupil is not centered in the iris.  If the pupil is off only a small amount, the dogs seem to cope well, but the issue comes when the condition is more severe.

Micropthalmia - an abnormally small eye (this is the most common defect seen in Homozygous Merles)

One thing to remember is that not all dogs are affected by deafness or blindness and very few dogs are affected by both.

The amount of color on a Double Merle dog can vary.  They can have no pigment (coloring) whatsoever, or they can have quite a bit of coloring (pigmentation).

Wyndlair Avalanche is a Blue Merle Tricolor Collie, on the website they say he is a White Merle.  This dog is an active stud dog, and has produced many champion collies.  But that does not give anyone a reason to intentionally breed two merle dogs, knowing there will be defects in the dogs.  Even if it wasn't intentional, you should not keep a pup from the cross, especially a Double Merle puppy that was blind, with the intention of using him as an active breeding dog!

There is no reason for anyone to purchase a Double Merle dog from a breeder, or the offspring of a Double Merle dog.  If you stop buying, they will have to stop breeding the Double Merles!  The only place you should get a Double Merle from is an animal rescue, a Double Merle rescue would be even better.  A reputable breeder would put the double merle puppies to sleep to prevent a life of suffering.

Introduction

As an aspiring dog breeder, I am very interested in the genetics of dogs.  Through this blog, I will be investigating  the genetics of dogs, especially Border Collies, and I will also be voicing my own opinion on things.  If you do not agree with my opinion, voice your own, or leave the blog.  Thanks for reading, and I would love to hear more information about things, etc.