Lucas Delgado
Chickens with crests on their heads are known as crested chickens. They are characterised by a tuft or crest of upward-pointing feathers on their heads. The development of the feather crest is based on the mutation Crest (Cr). This mutation alters the expression pattern of the cluster of HOXC genes on chicken chromosome 33. The mutation causes body feathers to replace the much smaller feathers that normally grow on their heads. Crested chickens are found in many breeds from all over the world, including the Appenzeller, Crèvecœur, Icelandic, Jinhuwu, Polish, Silkie, Sulmtaler, Sultan, and Chinese fatty chicken.
| Characteristics | Values |
|---|---|
| Definition | A group of ornamental chicken breeds characterised by a tuft or crest of upward-pointing feathers on the head |
| Origin | Netherlands, France, Italy, Poland, Russia, Western Balkans, Africa, Iceland |
| Breeds | Icelandic, Lyonnaise, Blue Breda, Altsteirer, Paduan, Polish, Crèvecœurs, Houdans, Appenzeller Spitzhaubens, Sultans, Jinhuwu, Silkie, Sulmtaler, Chinese fatty chicken |
| Weight | Medium-sized (4-7 lbs) to large (6-7 lbs) |
| Egg Colour | White, cream, brown |
| Egg Size | Small to large |
| Eggs per Year | 100-200 |
| Purpose | Dual (eggs and meat) |
| Temperament | Calm, docile, friendly, trusting, hardy in all environments |
| Mutation | The "Crest" (Cr) mutation alters the expression pattern of the cluster of HOXC genes on chicken chromosome 33 |
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What You'll Learn
- Polish chickens have vaulted skulls and are prone to brain injuries
- The crest gene mutation causes body feathers to replace head feathers
- The Crest phenotype is characterised by a tuft of elongated feathers
- The mutation alters the expression pattern of the HOXC gene cluster
- Crested chickens are found in Africa, Europe, and Iceland
Polish chickens have vaulted skulls and are prone to brain injuries
Chickens with crests on their heads are called crested chickens. They are a group of ornamental chicken breeds characterised by a tuft or crest of upward-pointing feathers on the head. The development of the feather crest is based on the mutation "Crest" (Cr). The mutation alters the expression pattern of the cluster of HOXC genes on chicken chromosome 33.
Polish chickens are a breed of crested chickens. They have vaulted skulls, which are misshapen, with a large knob or vault sticking up from the top. This misshapen skull results in a misshapen, unusual, “hourglass”-shaped brain. The skulls of Polish chickens often have holes, leaving the brain protected by only a thin layer of skin and feathers. This makes them vulnerable to brain damage and injuries.
One Polish chicken, Jennifer, displayed strange behaviour, with her head slowly drooping until it was almost on the floor. She has suffered brain damage, but fortunately, it is mild, and she is still functional enough to eat and roost. However, not every blow or peck to the head is fatal for vaulted-skull chickens. The severity of the brain damage that results from non-fatal injuries depends on the amount of brain swelling that occurs as a result of the injury. If the increased pressure causes their brain to swell through the holes in the skull, the chicken can suffer severe and probably fatal brain damage.
In addition to Polish chickens, vaulted skulls have also been observed in other crested chicken breeds such as the American Silkie. Silkies born with vaults are more likely to have larger crests as adults and be more popular. However, some breeders have noted that vaulted skulls do not have anything to do with crest size and may even be a defect that makes the birds very fragile.
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The crest gene mutation causes body feathers to replace head feathers
Chickens with crests, such as the Polish chicken, have a mutation in the Crest gene, which causes body feathers to replace the much smaller feathers that normally grow on their heads. This mutation alters the expression pattern of the cluster of HOXC genes on chicken chromosome 33. Specifically, it is associated with ectopic expression of HOXC8 in the cranial skin during embryonic development. The mutation causes an upregulation of HOXC gene expression in the skull tissue, resulting in larger feathers and an enlarged skull.
The phenotype of the Crest gene mutation is characterised by a tuft or crest of upward-pointing, elongated feathers on top of the chicken's head. This phenotype is similar to that seen in several wild bird species, such as cockatoos, which are known for their prominent crests. The appearance of the crest in chickens varies depending on the length and shape of the cranial feathers, with roosters having sharp-pointed feathers and hens having rounded feathers.
The inheritance pattern of the Crest gene mutation is autosomal incompletely dominant. This means that a chicken needs to inherit two copies of the mutated gene, one from each parent, to exhibit the crest phenotype. The mutation is not fully penetrant, as some chickens with only one copy of the mutated gene may still show a reduced form of the crest.
The development of the crest in chickens is likely related to the vaulted skull phenotype, which is characterised by a misshapen skull with a large knob on top. This skull deformity can lead to an hourglass-shaped brain and an increased vulnerability to brain injuries. The combination of the crest and vaulted skull traits may be two sides of the same genetic coin, with both traits influenced by the same HOXC gene mutations.
While the exact mechanism of crest formation is not fully understood, it is believed to involve the EPHB2 protein and its role in setting up feather orientation during embryonic development. The 'no crest' allele codes for a functional protein that transmits signals within the cell, while the 'crest' allele codes for a broken protein that cannot transmit signals. When a bird inherits two copies of the 'crest' allele, the resulting lack of signal transmission leads to the upside-down growth of neck feathers, forming a crest.
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The Crest phenotype is characterised by a tuft of elongated feathers
Chickens with crests, or crested chickens, are a group of ornamental chicken breeds characterised by a tuft or crest of upward-pointing feathers on their heads. The development of the feather crest is based on the mutation "Crest" (Cr). The mutation alters the expression pattern of the cluster of HOXC genes on chicken chromosome 33. The mutation causes body feathers to replace the much smaller feathers that normally grow on chickens' heads.
The HOXC cluster is not included in the current genome assembly for chickens. The molecular characterisation of the Crest causative mutation has to await until a method for assembling the chicken genome, particularly microchromosomes, is established. However, it is proposed that Crest is caused by a cis-acting regulatory mutation underlying the ectopic expression of HOXC8.
Crested chickens also have "vaulted skulls", which are misshapen, with a large knob or vault sticking up from the top. This results in an unusual, hourglass-shaped brain. Vaulted skulls are often filled with holes, leaving parts of the chicken's brain protected by only skin and feathers. Vaulted skulls and large crests are likely related traits. Because of their fragile skulls, Polish chickens are vulnerable to brain injury.
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The mutation alters the expression pattern of the HOXC gene cluster
Chickens with crests on their heads are known as crested chickens. They are a group of ornamental chicken breeds characterised by a tuft or crest of upward-pointing feathers on their heads. The development of the feather crest is based on the mutation "Crest" (Cr). The mutation alters the expression pattern of the cluster of HOXC genes on chicken chromosome 33.
The HOXC gene cluster is a group of related genes that specify regions of the body plan of a chicken embryo along its head-tail axis. Hox genes are arranged in clusters, and typically, their order on the chromosome is the same as the order in which they appear along the body. The Hox genes are so named because mutations in them cause homeotic transformations.
The mutation that causes the crest phenotype in chickens is associated with ectopic expression of HOXC8 in cranial skin during embryonic development. The HOXC8 gene showed a tissue-specific expression pattern in the cranial skin of birds carrying the Crest mutation. This results in the development of a tuft of elongated feathers on the head of the chicken, giving it a crested appearance.
The inheritance of the Crest phenotype is incomplete autosomal dominant. This means that the phenotype can be expressed even if only one copy of the mutated gene is inherited. The phenotype is characterised by a tuft of elongated feathers on the head of the chicken, giving it a crested appearance.
The expression of the HOXC8 gene during embryonic development leads to the formation of the crest in crested chickens. The mutation alters the expression pattern of the HOXC gene cluster, resulting in the ectopic expression of the HOXC8 gene in the cranial skin. This altered gene expression causes the development of the crest, which is a cluster of upward-pointing feathers on the head of the chicken.
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Crested chickens are found in Africa, Europe, and Iceland
Chickens with crests, or crested chickens, are a group of ornamental chicken breeds characterised by a tuft or crest of upward-pointing feathers on their heads. The development of the feather crest is based on the mutation "Crest" (Cr). This mutation alters the expression pattern of the cluster of HOXC genes on chicken chromosome 33, resulting in body feathers replacing the much smaller feathers that normally grow on their heads.
In Europe, crested chickens have a long history, with evidence suggesting their presence in England during Roman times. They became more widely known in the 19th century with the development of exhibition poultry breeding. Original crested chickens in Europe originate from various countries, including the Netherlands, France, Italy, Poland, Russia, and the Western Balkans.
In Iceland, chickens were introduced during the settlement of the island in the 10th century by the Norse. For a thousand years, the only chickens in Iceland were of a robust landrace variety. However, in the 1930s, other strains of chickens were imported, leading to crossbreeding and endangering the pure landrace population. Conservation efforts began in the 1970s to protect the native chicken population, and these efforts successfully led to the importation of genetically priceless birds to other countries, including the United States.
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Frequently asked questions
A crested chicken is a group of ornamental chicken breeds characterised by a tuft or crest of upward-pointing feathers on their heads.
The development of the feather crest is based on the mutation "Crest" (Cr). The mutation alters the expression pattern of the cluster of HOXC genes on chicken chromosome 33.
Yes, there are many different breeds of crested chickens, including the Icelandic, Appenzeller, Crèvecœur, Jinhuwu, Silkie, Sulmtaler, Sultan, and Chinese fatty chicken.
Crested chickens have a long history, with evidence of their presence in England during Roman times. They were also depicted in the Ornithologiae tomus alter of Ulisse Aldrovandi in 1600 and in the work of Dutch painters in the 17th century.
Yes, crested chickens with vaulted skulls may be more susceptible to brain injuries due to their misshapen skulls.
