SOME BACKGROUND

That is, genetics requires large numbers of individuals.

For plants this is easy:
Plants have large litters and they stay put, in places where they can be found, counted, and categorized.  Dogs are different.

Teaching an old dog new tricks has it's difficulties.  The answer to these limitations lies in a somewhat different type of genetic approach from the transmission genetics originated by Gregor Mendel.  This approach is known as  population genetics.

There are two main differences between population genetics and transmission genetics:
 

The necessity of using an existing population which is less than ideal and genetically more complex, imposes the need for studying more individuals when using population genetics instead of transmission genetics.

It is important therefore, to pick the best population that can be found in order to minimize the number of individuals required.
 

There are two major technical advances which have provided tools for population genetics.

In recent years, the ability to use DNA material to determine genotypes of large numbers of individuals has advanced as rapidly as the improvement in the power of computers.  As a result, during the last decade, population genetics has become a powerful approach to genetic questions.

Phenotypes can be very different, depending on whether one gene or many genes control the them.
 

The genetic rules for single gene phenotypes are rather simple and provide the mendelian inheritance with which we are familiar.  Every dog has two copies of each gene and a phenotype may be recessive ("r") or dominant ("D") depending on whether both chromosomes must have the right type of gene (e.g. brown) or whether it is enough to have only one copy which is correct (e.g. black).  The number of individuals in the population with these phenotypes will be in a proportion of roughly three dominant for every recessive provided that recessive and dominant types of genes are present in the population in equal numbers.

Multigene phenotypes are genetically much more complex.  A variety genes, often on different chromosomes, combine to produce different phenotypes.  Depending on which genes are present Phenotypes will differ.  Multigene combinations usually determine the "how much?" character of the phenotype, such as how big a dog might be, or how many puppies there may be in a litter, or yet again, how long a dog will live.  All of these are phenotypes of great interest to owners and breeders.

Multigene phenotypes are under investigation in the Georgie Project: