Essentials of the Living World 5th Edition by George Johnson

تمرين 1

Why Woolly Hair Runs in Families
The boy in the photo on the right does not cut his hair. His hair breaks off naturally as it grows, keeping it from getting long. Other members of his 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 flares up in certain families. The extensive pedigree below (drawn curved to fit the large families produced by the second and subsequent generations) records the incidence of woolly hair in five generations (indicated by the Roman numerals on the left) of a Norwegian family. As is the convention, affected individuals are indicated by solid symbols, with circles indicating females and squares indicating males. The pedigree will provide you with all 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?