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Both eumelanin and pheomelanin are derived from the amino acid:  

Which kind of sun tan lasts longer?

Based on genetic analysis of the MC1R gene, biologists estimate that body hair loss and brown skin appeared in the human line around:  

At any given time, 85-90% of your scalp hairs are in the _______ phase of the hair growth cycle.

All humans have roughly the same number of melanocytes in their skin and hair. The differences in skin color are the result of variation in the: Mark all that apply.  

Scalp hair can remain in the telogen phase for almost a year.

What hormone causes vellus hair to transform into terminal hair in certain areas of the body during puberty?  

Sunscreens with higher SPF do not last or remain effective on the skin any longer than lower SPF and must be reapplied as directed, usually every two hours.

Vellus hairs are thinner because, unlike terminal hair, they lack a:

While Mary is eating lunch at McDonald’s, her car is stolen.