Question

a horticulturalist wants to produce geraniums with specific characteristics. she knows that the trait of red flowers is governed by the allele r (rr and rr) and the trait of white flowers is governed by the allele r(rr).
the horticulturalist plans to cross a geranium that is true - breeding for red flowers with a geranium that is true - breeding for white flowers.
which punnett square best describes this cross?

Explanation:

Step1: Determine the genotypes of the parents

A true - breeding red - flowered geranium has the genotype \(RR\) (since it is homozygous for the red - flower allele). A true - breeding white - flowered geranium has the genotype \(rr\) (homozygous for the white - flower allele).

Step2: Analyze the gametes produced by each parent

The \(RR\) parent can only produce gametes with the allele \(R\). The \(rr\) parent can only produce gametes with the allele \(r\).

Step3: Set up the Punnett square

When we cross \(RR\) (parent 1) with \(rr\) (parent 2), in a Punnett square, one parent's gametes (\(R\) from \(RR\)) are on one side (say the vertical side) and the other parent's gametes (\(r\) from \(rr\)) are on the other side (say the horizontal side). Each box in the Punnett square is filled by combining the alleles from the corresponding row and column. So, all the offspring will have the genotype \(Rr\).

Answer:

The Punnett square with \(R\) (from the \(RR\) parent) on one side (two rows of \(R\)) and \(r\) (from the \(rr\) parent) on the other side (two columns of \(r\)), resulting in all \(Rr\) offspring (i.e., the first Punnett square shown in the problem description where each box is \(Rr\)) is the correct one.