Question

The horticulturalist crosses two geraniums from the f1 generation. look at the punnett square to see this cross. what ratio of red- to white-flowering plants would you expect to see in the phenotypes of the f2 generation?

Answer 1

Hi,

In Geranium plants  red flowers is given by the allele R that is dominant (so RR or Rr ) genotype will produce red flowers.

If we talk about the attached punnet square which i took from the exercise book, you can see that there was a cross made between two plants with heterozygous genotype for red flowers.

P1:                                             Rr X Rr

Gametes:                                R:  r : R : r

F1:                                            RR: Rr: Rr: rr

so there is 3: 1 in F1 offspring for red to white flowers.

Now the question is about  f2 generation, when we cross F1 generation suppose we do a cross of Rr and rr from F1 generations let us see what happens.

F1:                                          Rr:         rr

Gametes:                             R: r:     r: R

F2 :                                     Rr : rr: Rr: rr

Rr: Red flowers

rr: White flowers:

So the ratio in F2 generation will be 2 red : 2 white. Please see attached punnet squares (first one for question) and the second one of F1 cross for better understanding.

Hope it help!