Suggest one reason why low doses of a drug is used in Phase 1 clinical trials

What are some possible short and long term medical concerns for crew members on longer space exploration trips

Pink fur (p) is dominant to purple fur (p) in hamsters. two heterozygous pink hamsters are crossed. what is the probability that these two parents will have an offspring with purple fur? 2/4, 1/2 or 50% 1/4 or 25% 3/4 or 75% 4/4 or 100% there is no chance for this type of offspring

Vessels draining the myocardium of the heart, open primarily ,into which chamber?