Questions and Problems 



93 



of the Fi with the male and with the female parents? These genes are 

 in autosomes. 



4. In hmiian beings, albinos are homozygous for the recessive gene, 

 c, the allele of normal. A normal man marries an albino woman. They 

 have one child, who is an albino. From this one child, can we tell 

 whether the father was homozygous or heterozygous? If the one child 

 was normal, what would we know of the father? 



5. In Drosophila melanog aster, vestigial wing is recessive to normal. 

 A geneticist has three wild-type flies. He crossed fly A with fly B and 

 got 112 wild-type offspring; fly A crossed with fly C gave 83 wild-type 

 and 30 vestigial; fly B crossed with fly C produced 79 wild-type flies. 

 What would be the expected phenotypic and genotypic ratios when each 

 of these flies was crossed with a vestigial ? 



6. In phlox, the gene for entire petals is incompletely dominant to its 

 allele which produces incised, or cmpidata, petals. The heterozygote is 

 intermediate and is called fimbriata. What are the ofl"spring from the fol- 

 lowing crosses: fimbriata X entire; fimbriata X fimbriata; entire X cus- 

 pidata ; cuspidata X fimbriata ; entire X entire ; cuspidata X cuspidata ? 



7. If all the blue Andalusian fowls died out, could new ones be pro- 

 duced? How? If aU black and white fowls were killed, but blue Anda- 

 lusians were not, could new black and new white ones become estab- 

 lished? How? 



8. Congenital cataract in human beings is dominant over normal 

 (absence of congenital cataract). It may sometimes be cured by an 

 operation. A normal woman marries a man homozygous for the gene 

 for cataract. They have two children, A and B. The man then has an 

 operation and the cataracts are successfully removed. After that they 

 have two more children, C and D. What would be the expected pheno- 

 types of A, B, C, and D? 



9. B. J. Chumlea has reported a pedigree of otosclerosis, a form of 

 deafness due to abnormal bone growth, in human beings. From this 

 pedigree, which includes four generations, would you consider the trait 

 as due to a dominant or to a recessive gene? 



O 



50 



^ 



•tO 4 4 ■ 



cMD D D nan 



■o 



D D 6 



Din D o n 6 6 



D D n 



