Answer :
To solve this problem, we need to determine the outcomes of a genetic cross using a Punnett square. Here’s how we can do it step by step:
1. Identify the Genotypes:
- The horticulturalist is crossing two geraniums: one that is true-breeding for red flowers and one that is true-breeding for white flowers.
- A true-breeding red-flowered plant has the genotype `RR`. This means it has two dominant alleles for red flowers.
- A true-breeding white-flowered plant has the genotype `rr`. This means it has two recessive alleles for white flowers.
2. Set Up the Punnett Square:
- A Punnett square is a grid that shows the possible genotypes of the offspring from a genetic cross.
- For this cross, we place the alleles of one parent across the top and the alleles of the other parent down the side. Since the red-flowered plant is `RR`, we place `R` and `R` across the top. For the white-flowered plant, which is `rr`, we place `r` and `r` down the side.
3. Fill in the Punnett Square:
- Combine the alleles from each parent to fill in the squares.
- The first square combines the first `R` from the red-flowered plant with the first `r` from the white-flowered plant, resulting in `Rr`.
- The second square combines the first `R` from the red-flowered plant with the second `r` from the white-flowered plant, also resulting in `Rr`.
- The third square combines the second `R` from the red-flowered plant with the first `r` from the white-flowered plant, resulting in `Rr`.
- The fourth square combines the second `R` from the red-flowered plant with the second `r` from the white-flowered plant, resulting in `Rr`.
4. Interpret the Results:
- All the offspring (all four squares) have the genotype `Rr`.
- This means all the offspring will have red flowers, as the `R` allele is dominant over the `r` allele.
Therefore, the Punnett square shows that all offspring from this cross will be heterozygous `Rr` and will display red flowers. In terms of a Punnett square layout, it looks like this:
[tex]\[
\begin{array}{|c|c|c|}
\hline
& r & r \\
\hline
R & Rr & Rr \\
\hline
R & Rr & Rr \\
\hline
\end{array}
\][/tex]
All offspring are `Rr`.
1. Identify the Genotypes:
- The horticulturalist is crossing two geraniums: one that is true-breeding for red flowers and one that is true-breeding for white flowers.
- A true-breeding red-flowered plant has the genotype `RR`. This means it has two dominant alleles for red flowers.
- A true-breeding white-flowered plant has the genotype `rr`. This means it has two recessive alleles for white flowers.
2. Set Up the Punnett Square:
- A Punnett square is a grid that shows the possible genotypes of the offspring from a genetic cross.
- For this cross, we place the alleles of one parent across the top and the alleles of the other parent down the side. Since the red-flowered plant is `RR`, we place `R` and `R` across the top. For the white-flowered plant, which is `rr`, we place `r` and `r` down the side.
3. Fill in the Punnett Square:
- Combine the alleles from each parent to fill in the squares.
- The first square combines the first `R` from the red-flowered plant with the first `r` from the white-flowered plant, resulting in `Rr`.
- The second square combines the first `R` from the red-flowered plant with the second `r` from the white-flowered plant, also resulting in `Rr`.
- The third square combines the second `R` from the red-flowered plant with the first `r` from the white-flowered plant, resulting in `Rr`.
- The fourth square combines the second `R` from the red-flowered plant with the second `r` from the white-flowered plant, resulting in `Rr`.
4. Interpret the Results:
- All the offspring (all four squares) have the genotype `Rr`.
- This means all the offspring will have red flowers, as the `R` allele is dominant over the `r` allele.
Therefore, the Punnett square shows that all offspring from this cross will be heterozygous `Rr` and will display red flowers. In terms of a Punnett square layout, it looks like this:
[tex]\[
\begin{array}{|c|c|c|}
\hline
& r & r \\
\hline
R & Rr & Rr \\
\hline
R & Rr & Rr \\
\hline
\end{array}
\][/tex]
All offspring are `Rr`.
