Answer :
To solve the question about the geranium cross, let's break it down step by step:
1. Understanding the Problem:
- We are crossing two geranium plants: one true-breeding for red flowers and one true-breeding for white flowers.
- The red flower trait is governed by the allele "R." A geranium with red flowers can have either "RR" or "Rr" genotypes.
- The white flower trait is governed by the allele "r," and the plant must have the genotype "rr" to have white flowers.
2. Analyzing the Cross:
- A true-breeding red geranium has the genotype "RR" (homozygous dominant).
- A true-breeding white geranium has the genotype "rr" (homozygous recessive).
- When these two plants are crossed, each parent contributes one allele to the offspring.
3. Setting Up the Punnett Square:
- The red parent (RR) can only contribute an "R" allele.
- The white parent (rr) can only contribute an "r" allele.
- Therefore, all offspring will receive one "R" allele from the red parent and one "r" allele from the white parent.
4. Results of the Cross:
- All the offspring will have the genotype "Rr."
- With the genotype "Rr," the offspring will exhibit the red flower trait, as "R" is dominant over "r."
5. Matching the Punnett Square to the Answer Choices:
- We are looking for the Punnett square that shows this cross: one row or column of "Rr" results, which indicates all offspring are heterozygous.
- The Punnett square that fits this situation is:
```
\begin{tabular}{|c|c|c|}
\hline & [tex]$r$[/tex] & [tex]$r$[/tex] \\
\hline[tex]$R$[/tex] & [tex]$Rr$[/tex] & [tex]$Rr$[/tex] \\
\hline
\end{tabular}
```
- This corresponds to choice B.
Therefore, the correct Punnett square that best describes the cross of a true-breeding red flowering geranium with a true-breeding white flowering geranium is choice B.
1. Understanding the Problem:
- We are crossing two geranium plants: one true-breeding for red flowers and one true-breeding for white flowers.
- The red flower trait is governed by the allele "R." A geranium with red flowers can have either "RR" or "Rr" genotypes.
- The white flower trait is governed by the allele "r," and the plant must have the genotype "rr" to have white flowers.
2. Analyzing the Cross:
- A true-breeding red geranium has the genotype "RR" (homozygous dominant).
- A true-breeding white geranium has the genotype "rr" (homozygous recessive).
- When these two plants are crossed, each parent contributes one allele to the offspring.
3. Setting Up the Punnett Square:
- The red parent (RR) can only contribute an "R" allele.
- The white parent (rr) can only contribute an "r" allele.
- Therefore, all offspring will receive one "R" allele from the red parent and one "r" allele from the white parent.
4. Results of the Cross:
- All the offspring will have the genotype "Rr."
- With the genotype "Rr," the offspring will exhibit the red flower trait, as "R" is dominant over "r."
5. Matching the Punnett Square to the Answer Choices:
- We are looking for the Punnett square that shows this cross: one row or column of "Rr" results, which indicates all offspring are heterozygous.
- The Punnett square that fits this situation is:
```
\begin{tabular}{|c|c|c|}
\hline & [tex]$r$[/tex] & [tex]$r$[/tex] \\
\hline[tex]$R$[/tex] & [tex]$Rr$[/tex] & [tex]$Rr$[/tex] \\
\hline
\end{tabular}
```
- This corresponds to choice B.
Therefore, the correct Punnett square that best describes the cross of a true-breeding red flowering geranium with a true-breeding white flowering geranium is choice B.
