Ask A Scientist Molecular Biology Archive

name         Leonard D.
status       educator
age          40s

Question -   Does the amino acid Tyrosine play any role in how hair
color adheres  to the hair shaft?
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Helen Kreutzer and Adrianne Massey have come out with a new edition of their
book "Recombinant DNA and Biotechnology" .  In this book they include an
activity that deals with the pigmentation of Labrador retrievers.  On page
366 of the teacher's edition:
"Pigmentation in dogs and other mammals (including you) is caused by the
relative amounts and types of two classes of pigment:  eumelanin and
phaeomelanin.  The eumelanins are black and brown pigments and phaeomelanins
are red and yellow.  Both.. are synthesized in pigment-producing cells called
melanocytes......First the enzyme tyrosinase converts the amino acid tyrosine
to dopaquinone.  If tyrosinase-related protein 2 is present, it converts the
dopaquinone to a version of eumelanin that has a brown color.  If the enzyme
tyrosinase related protein 1 is present, it converts the brown version of
eumelanin into the final black pigment.  If there is no TRP-1, the color
remains brown.
There is more to this activity that shows students why yellow color is 
produced and why albinos result as well.

vanhoeck
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