The vertebrae and cartilaginous discs of the spine are parts of which body system?
a. circulatory system
b. excretory system
c. muscular system
d. skeletal system

Red–green color blindness is an x-linked recessive trait in humans. polydactyly (extra fingers and toes) is an autosomal dominant trait. martha has normal fingers and toes and normal color vision. her mother is normal in all respects, but her father is color blind and polydactylous. bill is color blind and polydactylous. his mother has normal color vision and normal fingers and toes. if bill and martha marry, what proportions of children with specific phenotypes would they be expected to produce? the answers only include the proportions of some of the possible phenotypes; other phenotypes are also expected to occur but are not included.