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Genetic engineering

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How the wild chicken became the modern broiler

An international team of researchers led by scientists at Uppsala University in Sweden have achieved a breakthrough in genetic studies of domestic animals by demonstrating the genomic evolution of the modern chicken. The results are published in the journal 'Nature'.

A.R. | 12 march 2010

The Uppsala University study describes how selective breeding led to the wild chicken becoming the modern food product found in markets. Today, chicken is not only probably the most popular meat in the world, but is the most important and cost-effective source of animal protein.

The genome sequence of the chicken was first established in 2004 by a research team that used a single female genome from a breed of chicken called red jungle fowl, the wild ancestor of the modern chicken. Their research involved studying the genome sequence of both the red jungle fowl and eight different populations of the modern domestic chicken. This is the first study ever where the genetic diversity within and between populations are examined across the whole genome.
When animals are bred to improve their genes, something called a 'selective sweep' occurs. This is when a favourable gene mutation becomes fixed in a species. The researchers found that there was a selective sweep at the TSHR (thyroid stimulating hormone receptor) gene in chickens. In vertebrates, TSHR has a crucial role in metabolic regulation and the timing of reproduction as a response to changes in day length. In wild animals this is strictly controlled, preventing overpopulation by a particular species, but it has been drastically altered in modern chickens so they can lay eggs all year round.

A second selective sweep in chickens involved the TBC1D1 gene that had previously been associated with obesity in humans. The TBC1D1 protein is involved in the regulation of glucose update in muscle cells. The study shows that billions of broiler chickens worldwide carry a mutant form of the TBC1D1 gene.

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