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] ([tex]rr[/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. 2 red: 2 white
B. all red
C. 1 red: 3 white
D. 3 red: 1 white

To determine the expected ratio of red-to-white flowering plants in the F2 generation, we need to analyze the Punnett square provided for the genetic cross.

Let's break it down:

1. Understanding the Alleles:
- Red flowers are governed by the allele `R`, and can be expressed in genotypes `RR` and `Rr`.
- White flowers are governed by the allele `r`, and are expressed in the genotype `rr`.

2. Setting up the Punnett Square:
- The two geraniums from the F1 generation have the genotypes `Rr`.
- We cross these two `Rr` plants:
- Gametes produced can be either `R` or `r`.

3. Filling in the Punnett Square:
- The Punnett square shows the possible genotype combinations from this cross:

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

- From this, the genotypes are: `RR`, `Rr`, `Rr`, and `rr`.

4. Determining Phenotypes:
- Red Flowers: This phenotype would result from the genotypes `RR` and `Rr`.
- `RR` and `Rr` both represent the red flower phenotype.
- We have 3 possibilities here: `RR`, `Rr`, `Rr`.
- White Flowers: This phenotype would result from the genotype `rr`.
- Only `rr` represents the white flower phenotype.
- We have 1 possibility: `rr`.

5. Calculating the Phenotypic Ratio:
- Count the number of red-flowered plants: 3 (`RR`, `Rr`, `Rr`).
- Count the number of white-flowered plants: 1 (`rr`).

Therefore, the expected phenotypic ratio of red to white flowering plants in the F2 generation is 3 red : 1 white.