introduction genetics

introduction to genetics

To understand the next pages about color and coat, some knowledge about genetics is required. In each cell of a living being are chromosomes, where all information about the appearance of the plant, animal or human is stored. Chomosomes come in pairs, one originating from the father and one from the mother. The part of the chromosome that carries the information for a certain attribute is called gene (plural genes), like the genes for haircolor, the gene for blue eyes. The place on the chromosome where this gene is located, is called the locus (plural loci).

Mendel

Over the course of time, many genetic factors have been located and named and work continues today in many genome projects. The monk and scientist Mendel, was the first to do this systematicly. In 1957, Clarence C. Little wrote the book "The inheritance of Coat Color in Dogs", and we still use the letters he gave to the various color genes.

dominant or recessive

There are both dominant and recessive genes; if both types genes are present, only the dominant one will show. We write the dominant gene with a capital, the recesive genes with a small letter. There is not always a dominant and recessive gene, in some cases a combination of two different genes gives an attribute in between the other two, which is called intermediate. For example in some flowers there are the colors white and red. If a plant has both genes for red and white, its color will be pink.
Some genes can affect how other genes may or may not be expressed, so a certain allele may only show if an other allele from an other locus is present (or adversely, show only in the absence of an allele on that locus). Those genes that determine appearance or lack of appearance by other genes are called epistatic genes.

terminology

Appearance is called phenotype, while the genetic truth (genetic composition) is called genotype.
If the genes for a particular attribute or trait are the same it is said to be a homozygote for that attribute/trait. However, if the two genes for a particular trait or attribute differ, it is said to be a hetrozygote for this attribute/trait.
The different genes for a certain attribute are called alleles. All alleles from a certain locus together are called a series; and within the series, the different alleles are named in sequence of dominance (the dominant allele first).

I hope this is enough explanation to understand the following pages. If not, you can send me your question by e-mail at info (@) xin-feng.nl, and I will try my best to answer you.

sources

The following pages provide a summary of the chapters about color and coat from the Dutch book "De Chow Chow in Nederland", written by Janneke Leunissen - Rooseboom, based on information provided by Mona Selbach (Norway).
I have added recent information from a specialist in this field, Professor Sheila M. Schmutz Ph.D., who was so friendly to point out a few mistakes in these pages. She works at the University of Saskatchewan and has a great website about dogcolors.