The Living World 6th Edition by George Johnson, Jonathan Losos,William Ober,Claire Garrison

تمرين 9

Why Woolly Hair Runs in Families
The woman in the photo on the right does not cut her hair. Her hair breaks off naturally as it grows, keeping it from getting long. Other members of her family have the same sort of hair, suggesting it is a hereditary trait. Because of its curly, fuzzy texture, this trait has been given the name "woolly hair."
While the woolly hair trait is rare, it fl ares up in certain families. The extensive pedigree below (drawn curved so as to fi t in the large families produced by the second and subsequent generations) records the incidence of woolly hair in fi ve generations (the Roman numerals on the left) of a Norwegian family. As is the convention, affected individuals are indicated by solid symbols, with circles females and squares males. The pedigree below will provide you with the information you need to discover how this trait is inherited within human families.

Making Inferences
a. Is woolly hair sex-linked or autosomal
b. Is woolly hair dominant or recessive
c. Is the woolly hair trait determined by a single gene, or by several