A horticulturalist wants to produce geraniums with specific characteristics. She knows that the trait of red flowers is governed by the allele [tex]$R$[/tex] ([tex]RR[/tex] and [tex]Rr[/tex]), and the trait of white flowers is governed by the allele [tex]$r$[/tex]. The horticulturalist crosses two geraniums from the F1 generation.

Look at the Punnett square to see this cross:

[tex]\[

\begin{array}{|c|c|c|}

\hline & R & r \\

\hline

R & RR & Rr \\

\hline

r & Rr & rr \\

\hline

\end{array}

\][/tex]

Which ratio of red-to-white flowering plants would she expect to see in the phenotypes of the F2 generation?

A. All red
B. 3 red : 1 white
C. 2 red : 2 white
D. 1 red : 3 white

To solve this problem, let's first understand what the Punnett square tells us about the genetic cross for the geraniums.

The alleles involved are:
- [tex]$ R $[/tex] for red flowers
- [tex]$ r $[/tex] for white flowers

The Punnett square for the cross is as follows:

[tex]\[
\begin{array}{|c|c|c|}
\hline
& R & r \\
\hline
R & RR & Rr \\
\hline
r & Rr & rr \\
\hline
\end{array}
\][/tex]

From this Punnett square, we can derive the following genotypes for the offspring:
1. [tex]$ RR $[/tex]
2. [tex]$ Rr $[/tex]
3. [tex]$ Rr $[/tex]
4. [tex]$ rr $[/tex]

Now, we count the phenotypes:
- Red flowers come from genotypes [tex]$ RR $[/tex] and [tex]$ Rr $[/tex].
- White flowers come from genotype [tex]$ rr $[/tex].

Counting the phenotypes, we have:
- Red flowers (from [tex]$ RR $[/tex] and [tex]$ Rr $[/tex]): 3 occurrences (1 [tex]$ RR $[/tex] and 2 [tex]$ Rr $[/tex])
- White flowers (from [tex]$ rr $[/tex]): 1 occurrence

Thus, the ratio of red-to-white flowering plants is 3 red to 1 white. Therefore, the predicted ratio of phenotypes in the F2 generation is 3 red to 1 white.