Alena Patrick, age 12, of Vancouver, British Columbia, Canada, for her question:

WHY ARE WHITE MICE USED IN MEDICAL RESEARCH?

White laboratory mice are used for scientific and medical research because they can reproduce very quickly, and it is possible for many generations to be studied over a rather short period of time.

A female mouse will be able to have young when it is only 45 days old. A female mouse will then be able to give birth every 20 to 30 days. She carries her young in her body for 18 to 21 days before they are born.

Newborn mice are completely helpless at birth. But in 10 days their bodies are covered with fur and their eyes are open when they are 14 days old. When they are about three weeks old, the babies move out on their own since their mother will be about ready to have from four to seven more new babies.