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]rr[/tex].

A horticulturist crosses two geraniums from the F1 generation. Look at the Punnett square to see this cross.

[tex]\[
\begin{tabular}{|c|c|c|}
\hline
& R & r \\
\hline
R & RR & Rr \\
\hline
r & Rr & rr \\
\hline
\end{tabular}
\][/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. 1 red: 3 white
C. 3 red: 1 white
D. All red

To determine the ratio of red to white flowering plants in the F2 generation, let's analyze the results from the Punnett square provided:

1. Genotypes from the Punnett Square:
- The Punnett square shows the possible combinations of alleles from two heterozygous parents (Rr x Rr).
- The combinations listed are:
- RR
- Rr (there are two occurrences of this)
- rr

2. Phenotype Explanation:
- Red Flowers: The genotype for red flowers includes both [tex]$RR$[/tex] and [tex]$Rr$[/tex]. This is because the presence of at least one dominant allele [tex]$R$[/tex] results in red flowers.
- White Flowers: The genotype for white flowers is [tex]$rr$[/tex], as it requires two recessive alleles (only this combination results in white flowers).

3. Counting Phenotypes:
- Red Flowers: There are 3 combinations that result in red flowers (1 RR and 2 Rr).
- White Flowers: There is 1 combination that results in white flowers (1 rr).

4. Resulting Ratio:
- This gives us a 3:1 ratio of red to white flowering plants.

Therefore, the horticulturalist would expect to see a phenotypic ratio of 3 red to 1 white in the F2 generation.