By convention, P stands for the parental generation.  The offspring are called the "first filial generation," abbreviated F1.  If these F1 offspring are crossed, their offspring are called the "second filial generation," designated F2.  Note the following diagram.

          P  X  P       and      F1  X  F1

             F1                             F2

e.  If two of the F1 mice are bred with one another, what will be the genotypic and phenotypic ratios of the F2?

Genotypic Ratio: _______________________________________

Phenotypic Ratio: _______________________________________

6.  The presence of horns on Hereford cattle is controlled by a single gene.  The hornless (H) condition is dominant over the horned (h) condition. A hornless cow was crossed repeatedly with the same horned bull.  The following results were obtained in the F1 offspring:

    8 hornless cattle

    7 horned cattle

What are the genotypes of the parents?

cow 

bull  

7.  In fruit flies, red eyes (R) are dominant over purple eyes (r).  Two red-eyed fruit flies were crossed, producing the following offspring:

    76 red-eyed flies

    24 purple-eyed flies

           a.  What is the approximate ratio of red-eyed to purple-eyed flies?

b.  Based upon your experience with previous problems, what two genotypes give rise to this ratio?

c.  What are the genotypes of the parents?

d.  What is the genotypic ratio of the F1?

e.  What is the phenotypic ratio of the F1?