Eukaryotes Genomes - GALLUS GALLUS

Gallus gallus (red junglefowl) is native to Southern Asia, particularly the jungles of India however they spread all over the world when people domesticated the chicken. Their natural habitat is thick secondary forest or lush belukar. Gallus gallus is an herbivore and insectivore and belongs to the same species as the world's domesticated chicken flocks.

Their plumage is gold, red, brown, dark maroon, orange, with a bit of metallic green and grey. There are also some white and olive feathers. Two white patches, shaped like an ear, appear on either side of the head. Gallus gallus can be distinguished from other chickens not only by these white patches, but also by the greyish feet. The red junglefowl can measure up to 70 centimeters in length. They have a total of fourteen tail feathers. Rooster tails can be almost 28 centimeter in length.The red junglefowl rooster is said to be more brilliantly coloured that its tame relative. During June to October, G. gallus moults into an eclipse plumage. An eclipse plumage is, for male, black long feather across the middle of his back and slender red-orange plumes on the rest of his body. For a female, an eclipse plumage cannot be distinguished, but she does moult. The female red junglefowl is leaner than tame hens.

The breeding season of the red junglefowl is spring and summer. An egg is laid each day. For twenty-one days before hatching, the chick will develop inside of the egg. On the first day, the heart and blood vessels of the chick develop and start to work. At the end of the first day, the head starts to take shape. By the fourth day, all organs of the future chick are present. On the fifth day, external sex structure develops. By the thirteenth day, the skeleton begins to calcify using the calcium from the eggshell. From the time when the egg is laid until hatching, the chick feeds on the yolk that surrounds it. The yolk penetrates the chick's body by the umbilicus. On the twenty-first day, the chick, now fully developed, starts to break through the thin shell. This action can take anywhere from ten to twenty hours. By four to five weeks of age, the chicks are normally fully feathered. At five months old, the chicks reach sexual maturity. The females reach sexual maturity a little later than the males. They can live up to ten years.

Chickens practice evolutionary quality control and mother hens are the architects of the species, females can be coerced into copulating and have limited choice in their male partners but they have evolved a mechanism to control paternity and by making fathers out of the dominant roosters, mother hens are giving their chicks the best possible start in life. Studies have shown that dominance has a genetic component, the offspring of top roosters are more likely to grow up to be leaders than are those of low-ranking males. Male chickens can mate with females as often as they like and still hope to spread their genes far and wide because they can control how much sperm they expend during a sexual encounter, allowing them to use more or less depending on social and environmental factors. Two important factors are the competition-whether other roosters are mating with the same hen-and whether a rooster has already mated with a particular hen. Roosters distribute their sperm resources strategically according to several factors, including the reproductive value of the female, by contrast, subordinate roosters invest less sperm if several dominant males are mating with the same hen, realising they have little chance of success, they save their sperm for another occasion. Hens however have the roosters outwitted, they can squirt semen back on the assailant before he even pulls away; the male assumes everything went according to plan and has no reason to retaliate, during studies hens consistently retained the sperm of the one or two dominant roosters in the group and ejected all other, thus maintaining high quality offspring. The researchers are testing whether females grow bored mating with the same male. Early results indicate that they do!

The chicken, the Red Jungle Fowl, is the first bird to have its genome sequenced and is one of the premier non-mammalian vertebrate model organisms. Scientists completed the one-year project on schedule but with a new sense of urgency because of recent outbreaks of bird flu that have affected millions of chickens worldwide. The chicken genome isn't likely to answer questions about the bird flu or yield solutions immediately but in the years ahead researchers can hunt for genes in chickens that may protect against certain types of infections or make a bird susceptible to a virus. One example is that Chicken is a principal source of high-quality protein in the world diet and infectious diseases have always threatened the industry (eg Marek's disease, which causes lymphomas in susceptible chickens within weeks after infection). In many cases, these diseases have been controlled with vaccinations, scientists realise that we may have reached the limit of what vaccines can do and strategies need to be found that will enhance vaccines or provide alternative means of disease control. Specifically, scientist want to understand T-cell function in chickens because T-cells are so critical to immune function. Because the immune system in chickens is not fully developed until about two weeks after hatching if we could hasten the immune response of chickens, we could probably grow healthier chickens. It is important to understand how these systems work, regardless of whether we want to make better vaccines, or whether we want to raise chickens that are more disease resistant. Genomics is a powerful tool to study immune competence in birds.

References:

http://genome.wustl.edu/
http://animaldiversity.ummz.umich.edu/site/accounts/information/Gallus_gallus.html
http://www.genomenewsnetwork.org/articles/06_00/Meaningless_sex.shtml
http://www.udel.edu/PR/Messenger/00/4/biologist.html
http://www.findarticles.com/p/articles/mi_m1200/is_10_165/ai_114699700