FACTOID # 7: The top five best educated states are all in the Northeast.
 
 Home   Encyclopedia   Statistics   States A-Z   Flags   Maps   FAQ   About 
   
 
WHAT'S NEW
 

SEARCH ALL

FACTS & STATISTICS    Advanced view

Search encyclopedia, statistics and forums:

 

 

(* = Graphable)

 

 


Encyclopedia > Gray hair
Gray haired woman in New Dehli

Gray hair color typically occurs naturally as people age, usually turning their hair from its natural color to gray and then to white. More than 40 percent of Americans have some gray hair by their fortieth birthday, but white hairs can appear as early as childhood. The age at which graying begins seems to be almost entirely based on genetics. Sometimes people are born with gray hair because it is passed down genetically. Many people use hair dye to disguise the amount of gray in their hair. Image File history File links Metadata No higher resolution available. ... Image File history File links Metadata No higher resolution available. ... This article is about the urban region which is the capital of India. ... This article is about the general scientific term. ... Ashlie from Lizzie McGuire, with green hair Hair coloring products generally fall into four categories: temporary, semipermanent, deposit only/demi, and permanent. ...


The change in hair color is caused by the gradual decrease of pigmentation that occurs when melanin ceases to be produced in the hair root and new hairs grow in without pigment. Two genes appear to be responsible for the process of graying, Bcl2 and Mitf. The stem cells at the base of hair follicles are responsible for producing melanocytes, the cells that produce and store pigment in hair and skin. The death of the melanocyte stem cells causes the onset of graying.[1] In biology, pigment is any material resulting in color in plant or animal cells which is the result of selective absorption. ... Broadly, melanin is any of the polyacetylene, polyaniline, and polypyrrole blacks and browns or their mixed copolymers. ... For a non-technical introduction to the topic, see Introduction to Genetics. ... Mouse embryonic stem cells with fluorescent marker. ... This article or section does not cite its references or sources. ...


References

  1. ^ Nishimura EK, Granter SR, Fisher DE (2005). "Mechanisms of hair graying: Incomplete melanocyte stem cell maintenance in the niche". Science 307 (5710): 720-4. PMID 15618488. 

Science is the journal of the American Association for the Advancement of Science (AAAS). ...

See also

Hair color Hair color is the result of pigmentation due to the presence of the chemicals of melanin and phaeomelanin. ...


  Results from FactBites:
 
Gray (horse) - Wikipedia, the free encyclopedia (889 words)
Fleabitten gray is a color consisting of a white hair coat with small speckles or "freckles" of red-colored hair throughout.
However, if a gray horse is heterozygous (Gg), meaning it inherits one copy of the recessive gene (g), that animal may produce offspring who are not gray (depending on what color gene an offspring inherits from its other parent).
Some horses with a particular type of dun hair coat known as a "blue dun" or a grullo or grulla, appear to be a solid gray.
coloring gray hair (301 words)
If you use either of these products yourself, keep in mind that gray and white hair tends to be resistant, so you might have to leave the dye on for the maximum amount of time.
To blend in just a little gray, gentle semipermanents and temporary colors are good choices and are easy to apply at home (just beware of buildup); the gray will turn to highlights, and you'll look better than ever.
Gray hair usually is fairly coarse, and therefore somewhat resistant.
  More results at FactBites »

 
 

COMMENTARY     


Share your thoughts, questions and commentary here
Your name
Your comments

Want to know more?
Search encyclopedia, statistics and forums:

 


Press Releases |  Feeds | Contact
The Wikipedia article included on this page is licensed under the GFDL.
Images may be subject to relevant owners' copyright.
All other elements are (c) copyright NationMaster.com 2003-5. All Rights Reserved.
Usage implies agreement with terms, 1022, m