A chromosome is a piece of nucleoprotein (DNA or deoxyribonucleic acid) arranged into units, or genes which are responsible for the transmission of hereditary characteristics e.g. coat, colour, eye shape etc from one generation to the next. The individual genes occupy a fixed position on the chromosome. Every cell in the body contains a full set of pairs of genes; one of each pair comes from the sire, paternal genes and the other from the dam, maternal genes. Thus at mating the dogs sperm cell carries a full set of his chromosomes, representing each and every male gene. The bitch’s egg does likewise for the female genes, at fertilisation each cell receives a set of both types of genes. Genes are called the genetic blueprints; in other words they carry the plans to make up the new individual which arises from the fertilised egg.
However, occasionally something goes wrong with this process and genetic change, or mutation occurs, causing abnormalities; if the mutation is severe, genetic (inherited) disease may result.
If the particular genes which cause such changes can be identified, it may be possible to develop a DNA – based test for the particular disease, to identify not only affected individuals, but carriers as well enabling breeders potentially to control or even eradicate the disease by careful planning of breeding programmes. Thus building up a DNA databank for each breed is an important step forward in the fight against either a pre-existing inherited disease, or in the case of any new disease that may appear in the future.