French Bulldog DNA Information

Due to the reporting differences between DNA testing companies, your results may appear differently. Please read below to help convert your results

A-Locus (Pattern)

The A-locus has thee possible options (alleles), Ay – Fawn, At – Tan, a – solid.

Your DNA report may report this with both genes together (ie At/Ay) or by stating the copies individually ( At 1 copy, Ay 1 copy. A – no copies).

There will be a total of two of any of the mentioned alleles. You will take each of the present copies and put a slash between them. Here is an example:

Ay – no copies

At – 1 copy

a – 1 copy

This would be expressed as At/a.

If Ay is present, it will dominate the other genes and the Frenchie will be fawn. There is one exception to this, if (K-locus) brindle is present the At fawn gene will not appear as it works in combination. If the “At” gene is present with “a”, the “At” tan point will dominate and the Frenchie will have tan points. The “a” solid gene requires both copies to be present in order to be solid.

B-Locus (Brown / Testable Chocolate)

This gene is responsible for brown, known as testable chocolate, and works with other genes to create Isabella French Bulldogs. This is a recessive gene and you will require two copies in order for the French Bulldog to display the testable chocolate color. It will appear as b/b or state the B-locus has two copies. 1 copy would be a carrier.

B/B or N/N (no copies) – negative

B/b or b/N  (1 copy) – carries but does not display testable chocolate.

b/b  (2 copies) displays testable chocolate


The primary chocolate gene creates a different shade of brown compared to the B-Locus. Likewise, when combined with other visible colors will look different too. Cocoa is a recessive gene that will require both copies to produce the color.

N/N or CO/CO (no copies) – dog does not carry cocoa.

N/co (1 copy) – dog carries but does not display cocoa.

co/co (2 copies) – dog is visible cocoa.

D-Locus (Blue)

The dilute genes is responsible for reducing the saturation of coat color. By itself, it creates a blue French Bulldog. With other colors it will create Isabella and lilacs. It will appear as follows:

D/D or N/N (no copies) : dilute gene is not present.

D/d or d/N (1 copy) : dog carries dilute, but does not display is.

d/d (2 copies) : dog displays dilute (blue).

Some reports may read with a number such as d1 in place of d.

E-Locus (Cream)

The E-Locus is responsible for creating cream or white/yellow French Bulldogs. It requires two copies of “e” to become visible, and when present will dominate other colors and patterns. The E-Locus on a French Bulldog can also be Em which is a dark mask around the mouth. Some reports will split the E-Locus into one for “E” and one for “Em”, but you should have a total of two copies.  You can have a combination of a mask and color gene, such as Em/e, or just two masks or colors such as e/e. The presence of “Em” will result in a dark mask, “E” the typical black base for most Frenchie colors, or 2 copies of “e” produce a white or cream base. E/E (no copies of cream) – the dog does not carry cream. E/Em (1 copy of Mask)  or Em/Em (2 copies of Mask) – the dog will have a mask. e/Em (1 copy of Mask, 1 copy of Cream) – the dog will have a mask and carries cream but does not display it. e/E (1 copy of cream) – the dog carries cream but does not display it. e/e (2 copies of cream) – the dog is visible cream.

K-Locus (Black/Brindle)

The K-Locus is displayed a few different ways depending on the DNA testing company, but anytime one copy is present it will appear on the dog. It is not intensified with a second copy.  There are only two alleles, Kbr Brindle and Ky black. Here are the various ways we’ve seen it expressed: N/N or Ky/Ky (no copies) – The dog does not carry brindle. K/N, Kb/Ky, Kbr/Ky (1 copy) – The dog will be visible brindle. The dog can not be fawn even if Ay on the A-Locus. K/K, Kb/Kb, Kbr/Kbr (2 copies) – The dog will be visible brindle. The dog can not be fawn even if Ay on the A-Locus.

S-Locus (Piebald / Spotting)

The Piebald gene in French Bulldog requires both copies to be present to display. It will randomly remove pigments resulting in large areas of a different color. On most tests, it is represented as S or Sp to indicate the presence of a copy. To confuse things further, some testing copies us S to indicate a negative finding for Piebald. It is a dominant trait in some breeds, meaning it will appear with only one copy. However, with French Bulldogs, both copies are necessary to display the trait. N/N  -(no copies) – dog does not carry piebald. N/S or Sp/S (1 copy) – dog carries but does not display piebald. S/S or Sp/Sp (2 copies) – dog displays piebald. ** on some tests S/S indicates no copies, read the explanation on your results for clarification**


Merle French Bulldogs will have random spotting or mottling, and the pattern can be further predicted with other testing with certain companies. Merle is a dominant trait, so only one copy is required. It is also preferred as any time two copies of Merle are present on a dog, it can lead to hearing and vision problems so caution must be exercised when breeding Merles. N/N  (no copies) – dog is not merle. M/N (1 copy) – dog is merle. M/M (2 copies) – dog is merle and at great risk of hearing and vision deficiencies.

Long-Hair (Fluffy)

Long-haired or fluffy Frenchies, require two copies of the long-haired gene. There are different numbers sometimes associated with the gene (L1,L2,etc) but if two copies of this gene are present it will produce a fluffy Frenchie. L/L (no copies) – dog does not carry the gene. L/l (one copy) – dog carries, but does not display long hair. l/l (two copies) – dog is a long-haired or fluffy French Bulldog.


The Intensity gene has been connected to impact the saturation of the Yellow/Red, creating an extreme dilution. Research on this gene is improving every day, but currently, it is believed to impact coat color when both copies are present. I/I  (no copies) – dog does not carry intensity. I/i (1 copy) – dog carries, but is unlikely to show visibly. i/i (2 copies) – dog displays intensity.

Leave a Comment

Your email address will not be published. Required fields are marked *