Merle French Bulldogs – The Magic of Merle

By: Danielle Harris

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Merle French Bulldogs

Merle is a color coat pattern.

The merle pattern is characterized by irregularly shaped patches with diluted pigment while other patches on the coat are fully pigmented in color, and odd color eye or eyes.

Black Tan Merle French Bulldog
Black Tan Merle French Bulldog

Merles can come in ANY color.

This gene is dominant and only needs one copy to express. Because of this, 2 merles should never be bred together.

Animals that are “double merle,” a common term used for dogs that are homozygous (having two copies) of the merle (M/M) trait, are predominantly white and prone to several health issues.  

The chances of having puppies that develop health issues increase when two Merles are bred together.

It is recommended that a Merle dog only be bred to a non-merle/non-cryptic Merle dog. 

Cryptic merle dogs do not appear to be merle, but contain the merle gene. Many solid dogs are actually cryptic, also known as phantom, merles and can produce both merle and double merles if not careful.

Merle can affect all coat colors. Recessive red dogs can also be affected by Merle, but the patches are either hardly seen or (if the dog is a clear recessive red) are not visible at all.  Such as in Fawn and Cream.

In addition to altering base coat color, Merle also modifies eye color and the coloring of the nose and paw pads. The Merle gene modifies the dark pigment in the eyes, occasionally changing dark eyes to blue, or only part of the eye to blue. Since Merle causes random modifications, both dark-eyed, blue-eyed, and odd-colored eyes are possible.

Color on paw pads and nose may be mottled pink and black.

The chances of birth defects and health problems such as blindness and deafness is a significant concern when breeding 2 merles together.

When purchasing a pup from a litter that has merles, for breeding purposes, test the puppy to make sure it is not a cryptic merle.

Breeding Merles

2 Merles can be bred together but only if the length on both parents is short enough.

In general we DO NOT recommend breeding 2 merles together, as too many things can go wrong.

Merle and Pied can be bred together.

Harley Quinn - Harlequin Merle LPF Osiris x Elsa
Harley Quinn – Harlequin Merle LPF Osiris x Elsa
  • Dogs with N/N genotype are not expected to display a merle pattern. They cannot transmit this merle variant to any of their offspring.
  • Dogs with N/### or ###/### (### = any number from 200-280) may display a merle pattern. This pattern varies along a continuum. The amount of dilute patches is dependent on which merle allele(s) are present AND if the dog will show black/brown pigment (eumelanin) = NOT e/e at MC1R. In brief, eumelanic dogs with two copies of smaller allele sizes (lower numbers) display little to no merle pattern often referred to as “cryptic merle”. Eumelanic dogs with 1 or 2 copies of larger alleles (higher numbers) are expected to display the merle pattern.
Bean - Owned by Sharelle, Harlequin Merle LPF Osiris x Elsa
Bean – Owned by Sharelle, Harlequin Merle LPF Osiris x Elsa

Eumelanic dogs with one or two copies of the highest numbers (~270-280) display a dramatic dilution/white pattern referred to as harlequin. This is NOT the phenotype resulting from the gene variant identified as Harlequin (H) in the Great Dane. Breeding two dogs that possess any of the merle variants may produce “double merle” offspring (homozygous) which may be prone to health problems. Double merle dogs may have auditory, ophthalmologic, skeletal, and other defects and will transmit a merle variant to all of their offspring.

  • Dogs with N/###/### or ###/###/### (### = any number ranging from 200-280) have an additional merle allele likely resulting from the propensity of the repetitive DNA causing the merle phenotype to increase or decrease in size. Each individual cell still only has two copies. However, different cells of the body may have different sizes of alleles. The phenotypic impact of the additional allele cannot be predicted as distribution throughout the body may be variable. Similarly, it is possible for all alleles to be transmitted to offspring but depends on the alleles present in the egg and sperm cells, thus the heritability cannot be predicted.

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