The genetics of canine mating and reproduction, and what this means for breed lines

If you wish to breed from your bitch or use your dog to sire a litter, there are a lot of different considerations to bear in mind! First of all, you should critically assess the quality and temperament of your own dog, and that of their potential mate, ensure that there is a demand for their prospective litter, and do everything that you can to ensure that the dogs that you mate, and their subsequent litter, will be healthy.

This may mean using DNA tests or other forms of pre-breeding health screening to check for any health conditions or hereditary flaws prior to mating, but the genetics of mating dogs goes much further than just future health and health conditions! The match of dog and bitch chosen for mating will also determine factors such as the colouring, temperament, size and quality of the puppies, and this is something that professional breeders consider carefully, in order to ensure the progression and ongoing improvement of their future blood lines.

In this article, we will look at the basic genetics behind mating and reproduction, and how the match between dog and bitch affect the health, appearance and temperament of the puppies. Read on to learn more about canine genetics as they relate to breeding.

An introduction to canine genetics

Dogs carry a total of 39 chromosomes compared to humans, who have 46, and each chromosome is a package containing DNA information about different elements of the dog. Chromosomes come in pairs, of which one half of each pair is inherited from the dam and one the sire, and an additional, or anomalous chromosome can lead to various problems and conditions such as Downs Syndrome in people.

Each pair of chromosomes works in combination with each other, and other chromosome pairs too, to determine the traits that the dog possesses, and then, the combination of chromosomal traits of both the dam and the sire in turn, determine the traits of the puppies.

A good demonstration of this can be provided in the form of this article, which explains how the different gene pairs of Labrador retrievers affects the colour of their litters.

Dominant and recessive genes

Every single different trait that dogs possess, from their colour, temperament, sex, aptitudes, size and much more come about due to combination of chromosomes that they have in total. When two dogs are mated, their subsequent offspring will share traits from both parents, and what determines the traits that the puppies inherit comes down to the balance between dominant and recessive genes. This is what determines the colour of a puppy, when the two parent dogs are different colours, as well as a whole range of other things too.

Each individual trait that a puppy can inherit is composed of two alleles, one from each parent dog. If the two alleles are the same; for instance, if they both dictate, say, a yellow coat colour, then the puppy will be yellow. However, if the pup inherits two different alleles, one from each parent, the combination of dominant and recessive genes dictate the colour that the puppy will take.

If two different alleles are inherited and one of them is dominant and the other recessive in relation to each other, the dominant gene dictates the end result. However, whilst one allele may be dominant over another, a third allele may be dominant over one, both or neither, which is where things get really interesting! This means that it is never simple or intuitive to predict traits such as colour or size based on simple observation of the parent dogs alone.

Hereditary health conditions

Just as alleles control traits like colour, size and temperament, so too do they control other things, such as the inheritance of good health, or a predisposition to certain health issues.

Most pedigree breeds of dog have certain heredity predispositions to various health conditions, and mating two dogs that both carry the allele or mutation for such conditions greatly increases the chances of their puppies inheriting it too. Because the gene pool is limited within pedigree breeds where outcrossing to other breeds is not permitted as part of the breed standard, this increases the chances of a mating occurring between two dogs that carry the same hereditary genetic predisposition to the problem, and so, the chances of two alleles for the condition passing onto the pups.

This is why DNA testing and pre-breeding health screening is important for many pedigree dog breeds, as this can advise breeders about the genes that the puppies will inherit, and how likely this is to affect them.

On the flip side, outcrossing to other breeds can dilute the chances of heredity of breed-specific health problems, and strengthen the gene pool as a whole thanks to the benefits of hybrid vigour-however, doing this also dilutes the breed’s desirable traits as part of the breed standard too.

This means that outcrossing with another breed is very rarely permitted within pedigree breed standards, other than in cases where hereditary conditions have become so prevalent within the breed that it is virtually impossible to mate two dogs that are clear of the mutation that causes a particular problem.

What you can tell about a litter before it is born

Genetics is a beautiful science, in terms of its neatness and function as the building blocks of life. However, it is also a very complex field, and without a full genetic picture of the DNA of each dog and an expert in the field to analyse it, it can be very hard for the breeder or dog owner to know for certain what traits their litter will inherit from any potential combination of two parents.

Some elements can be identified simply from the physical appearance of the two dogs, and if both dogs share a trait-such as a common coat colour-it becomes easier to predict the outcome, notwithstanding anomalies that can lead to recessive genes pairing up to generate an entirely new variant!

Ultimately, canine genetics and DNA testing is largely concerned with improving the health of the subsequent litters and their chances of being healthy and not prone to developing a hereditary health condition themselves, and aside from this, the results in terms of colour, coat pattern, aptitudes and personality is something of a lucky dip.