Harlequin breeding is a fascinating and often heartbreaking endeavor. Even the genetic specialists do not fully understand the inheritance and traits of complicated harlequin/merle genes. At best harlequin breeding is an educated guess. At worst a "crap shoot" by uneducated people which can and does result in severely deformed puppies.

After having bred six litters our overall statistics are close to what one would expect. Each litter is hardly a large enough sample to give an accurate spread of the expected colours, so it is to be expected that an individual litter may yield more than expected or less. Thus the overall statistics (with a larger sample) are more important.

For the purposes of this exercise I have included three litters of another Dane breeder to gain a bigger sampler and thus a more accurate picture.

*Please note that the percentages below do not always add up to exactly 100%. This is due to puppies not being born in percentages :-) and also to keep the values at a simplistic level.

General Colours

Expected vs. Actual (sample of 83 puppies whelped)

Key:

Comparison of Expected vs. Actual percentage

As can be seen we have produced a higher than expected number of harlequins and blacks with a corresponding lower than expected number of merles and whites.

The reduced number of live whites (double merles) is exactly half of what one would expect. This is very much in line with the belief that the double merle is lethal in utero i.e. these puppies were conceived, but were reabsorbed. This also explains why harlequin to harlequin/merle litters are traditionally smaller than those found in the other colours (although this trend is not apparent in our statistics).

But if the double merle gene is lethal, then why do at least half of these double merles survive to whelping (albeit with defects)? Perhaps there is some kind of modifier at work, but ultimately the double merle is lethal and thus to be avoided.

The reduced number of merles, with a corresponding increase in harlequins and blacks is not understood. While this is beneficial for us, I would be fooling myself if I believed that this was by design. We have simply been lucky and over a larger sample one might see the actual results to match the expected results more closely.

The "holy grail" - five showmarked harlequins out of a litter of six.

Colour Distribution Patterns

In this section we will concentrate on colour distribution i.e. a black as opposed to a mantle or a heavily-marked harlequin as opposed to a showmarked harlequin* in terms of patch distribution. Other factors that influence harlequin showmarking (ticking and merle patches) will be ignored for this section.

*Although our standard does not call for patch distribution to be confined to specific areas on the harlequin for the purposes of this report I will deem the showmarked harlequin as a harlequin with any underlying homozygous mantle (SiSi) colour distribution pattern.

The puppies from harlequin X harlequin/merle matings throw a spanner in the works with regard to colour distribution. The double merle pups would have their colour distribution controlled by the S series, but the double merle tends to obliterate most of the distribution pattern. It is thus impossible to say what the S alleles would be on these dogs.

There are also puppies from harlequin X harlequin/merle matings that are not double merles, but are very under marked considering their expected S alleles.

I have elected to exclude the double merles altogether and make an educated guess with regard to the S alleles of the under marked pups. This could of course skew the figures, but nonetheless let's see!

For the purposes of simplicity we will use the following series of alleles based on distribution patterns seen in harlequin breeding:

All of the S series genes have plus and minus modifiers which control the amount of white. So although a dog may be SSi he could appear to be SiSi due to the modifiers.

The sample is based on a total of 78 whelps (excludes whites) as S series is impossible to discern.

Comparison of Expected vs. Actual percentage

The variance is very small and in all likelihood is probably due to a misinterpretation of the phenotype due to the action of modifiers.

While these figures do not appear to present anything exciting, they could indeed be beneficial in terms of determining the S series genotype and thereby increasing the odds of SiSi dogs i.e. dogs that are homozygous for the preferred patch distribution. This would increase the occurrence of showmarked harlequins as per the definition in the first paragraph.

Note: It is thought that homozygous dogs have a more symmetrical pattern in terms of patch distribution, so this is a factor worth considering when using a mantle in a breeding programme.

Page last updated: 18-09-08 11:02:04 PM

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