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On September 17th, 1998 the Ithaca Journal ran its first "Ask A Scientist!" article in which Professor Neil Ashcroft , who was then the director of CCMR, answered the question "What is Jupiter made of?" Since then, we have received over 1,000 questions from students and adults from all over the world. Select questions are answered weekly and published in the Ithaca Journal and on our web site. "Ask A Scientist!" reaches more than 21,000 Central New York residents through the Ithaca Journal and countless others around the world throught the "Ask a Scientist!" web site.

Across disciplines and across the state, from Nobel Prize winning scientist David Lee to notable science education advocate Bill Nye, researchers and scientists have been called on to respond to these questions. For more than seven years, kids - and a few adults - have been submitting their queries to find out the answer to life's everyday questions.

Previous Week's Question Published: 19 December, 2002 Next Week's Question
Tapetum causes dogs' eyes to reflect in different colors
Question
Why do some dogs eyes reflect red instead of yellow and does this have anything to do with their coat type?

Question
The colored reflection from the eyes of dogs comes from a layer of tissue at the back of the eye (the choroid) that contains blood vessels, brown pigment cells, and, in most dogs, a shiny cell layer (the tapetum) covering mostly the upper half. This tapetum probably improves animals' vision at night. It may be yellow, green, blue, orange, or variations in between those colors. So the tapetum is the usual source of a dog's eye reflection. Some dogs, though, have very small tapeta or none at all and they show a very dull reflection or none at all. In other dogs, especially dogs with certain hair coat colors (liver, orange-brown) or with blue eyes (irises), very little pigment is present in the back of the eye and the blood vessels that are normally hidden by this pigment are visible and make the reflection bright red.