Lecture_13-1-1 - In response to physiological control,...

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Lecture 13 – Notes Melanin pigments Responsible for many of the black yellow coloration you see in humans and animals. Hair color variation and skin color variation in humans result from different melanin concentrations. Bird colors in the black to yellow range also result from melanin deposition into feathers. Two types of melanin: Pheomelanins produce colors from light brown to red Eumelanins produce colors from black to dark brown Actual color of the feather does NOT result from total melanin content, but relative ratio of eumelanin to pheomelanin. Melanin is unique in that it is synthesized by the bird: Tyrosine Dopiquinone Either pheomelanin or eumelanin Tyrosinase is responsible for conversion from tyrosine to dopiquinone Albinism (complete lack of melanin coloration) results from malfunction of the tyrosinase. Feather follicle is associated with a melanocyte (melanin-producing cell). Melanosomes are organelles within the melanocyte containing melanin.
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Unformatted text preview: In response to physiological control, melanosomes move through the dentrites of the cell and into the feather creating feather colors. Melanocyte stimulating hormone – produced by the intermediate lobe of the pituitary in mammals, but birds lack this portion of the gland. Recently has been found that MSH is produced by the brain and eye of the bird. Drives the production and deposition of melanin in mammals – likely a similar influence in birds. Factors that contribute to melanin coloration: 1. Diet – intake of amino acids such as tyrosine and phenylalanine influence melanin coloration 2. Hormones Testosterone – generally testosterone increases degree and area of melanin coloration Estrogen – treatment of sexually mature males inhibits melanin coloration and produces female-like coloration. 3. Genetics...
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This note was uploaded on 04/08/2011 for the course POUL 3123 taught by Professor Navara during the Spring '09 term at UGA.

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Lecture_13-1-1 - In response to physiological control,...

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