Answer to Question #292442 in Genetics for Smilynne

Question

6. In what kind of situation would you want to perform a test cross? How would you do 

it?

7. Suppose that a certain breed of dogs has either floppy or pointy ears, and this trait 

is controlled by one gene with two alleles. Pointy ears are dominant over floppy 

ears. You have a pointy-eared dog and want to know whether it is homozygous or 

heterozygous. What would you do?

8. If you cross a true-breeding homozygous dominant individual with a true-breeding 

homozygous recessive individual, what will be the genotypes and phenotypes of the 

F1 generation? If you cross the F1 generation with each other, what will be the 

genotypes and phenotypes of the F2 generation?

9. In humans, having free earlobes (F) is completely dominant over having attached 

earlobes (f). If a man with free earlobes marries a woman with attached earlobes, 

and all of their kids have free earlobes, what is most likely the genotype of the 

father? Can you be completely sure of the father's genotype? Why or why not?

Answer 1

6.A testcross can be used to determine the organism's genotype. In a testcross, the individual with the unknown genotype is crossed with a homozygous recessive individual