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1. Pigeon Genetics

  Pigeons, like most life on earth, inherit characteristics form their parents. The traits or characteristics that can be inherited are myriad, from simple eye colour to complex temperament and homing ability. The basic mechanism by which traits are passed down from generation to generation was first studied by Gregor Mendel who studied pea plants in the 1850s. The basic principles he discovered has been explored and refined ever since. This field of study is called [classical] genetics. The next sections explain some of the basics concepts of genetics.

Basic Genetics

  Pigeons have a total of 80 chromosomes paired up to form 40 pairs. These chromosomes carry what are called genes. During the production of sperm and egg cells (a process called meiosis), the pairs split up and each egg or sperm cell only has 40 chromosomes. When the egg and the sperm fuse to form a new pigeon, the total of 80 is achieved again. Another way to look as it, is that for each chromosome pair, one chromosome comes from the female parent and one from the male parent.

  Here is an image to illustrate (a human karyotype):

Karyotype of a female human being (source - Wikimedia)

  Genes are responsible for all characteristics of the bird - colour, behavior and body conformation are all controlled by the genes passed down from the parents. Some genes are able to change the characteristics of the bird on their own, while other genes work together to form a specific trait. It is important to remember that some traits are so complex that their expression could be controlled by hundreds or even thousands of genes.

Mutation

  Mutations (changes in the structure of the gene - the DNA) happen naturally in nature and is the basic mechanism of evolution. Mutations of a gene cause changes to the traits of the organism. As a result of these mutations and selective breeding, humans have been able to create the hundreds of breeds of pigeons known today.

  Mutations can happen in a number of ways both natural and artificially induced. Natural mutations occur due to faulty translation of the DNA by a complex mechanism far beyond the scope of classical genetics. Mutations can also be caused by UV rays (e.g. cancerous mutations like melanomas in human beings), harmful chemicals (called carcinogens) or a number of other mechanisms.

Wild Type

 Geneticists need a standard to measure mutations against. This standard is called wild-type. This refers to the type of the organism in question, as it occurs in the wild. For pigeons wild-type is defined as the blue bar pigeon - the original wild form of the Rock Pigeon (Columba livia) that can still be seen in wild populations in western and southern Europe, North Africa, and into South Asia. (the Wikipedia article about the Rock Pigeon has more information).

Gender Determination

  Gender determination is also controlled by the chromosomes (at least in mammals and birds).  There is a special pair of chromosomes in these species.  This special pair of chromosomes are called the allosomes (or sex chromosomes) as opposed to the autosomes (the chromosomes not responsible for sex determination).
 
  The chromosomal sex determination in birds is known as ZW sex determination. This implies that the female birds have the two allosomes ZW and the males have the allosomes ZZ. (For human beings, this system is reversed, females are XX while males are XY).
 
  Those interested in the mechanisms of sex determination are again urged to have a look at the Wikipedia page .

What next?

  This page just a basic introduction to genetics (as it applies to pigeons mostly). More information can be found all over the web. See the links page for a few starting points.
  The next pages give some basic terminology and discuss specific mutations found in domesticated (and feral) pigeons.