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8. The table below lists the trials for fruit color where allele [tex]$R$[/tex] exhibits incomplete dominance over allele [tex]$R_1$[/tex].

\begin{tabular}{|l|l|}
\hline
Genotype & Phenotype \\
\hline
[tex]$R R$[/tex] & Red \\
\hline
[tex]$R_1 R_1$[/tex] & Yellow \\
\hline
[tex]$R R_1$[/tex] & Orange \\
\hline
\end{tabular}

Heterozygous fruit have orange phenotypes. What percent of offspring are expected to have an orange phenotype if the parent plants are orange [tex]$\left(R R_1\right)$[/tex] and yellow [tex]$\left(R_1 R_1\right)$[/tex]?

A. [tex]$25\%$[/tex]

B. [tex]$50\%$[/tex]

C. [tex]$75\%$[/tex]

D. [tex]$100\%$[/tex]

Sagot :

GinnyAnsweridn
To determine the percentage of offspring with an orange phenotype, we need to examine the possible genotypes resulting from crossing a parent with genotype [tex]\( RR_1 \)[/tex] (orange) and a parent with genotype [tex]\( R_1R_1 \)[/tex] (yellow).

### Step-by-Step Solution:

1. Identify the parent genotypes:
- Parent 1: [tex]\( RR_1 \)[/tex] (orange)
- Parent 2: [tex]\( R_1R_1 \)[/tex] (yellow)

2. Determine the possible allele combinations for the offspring:
- The first parent [tex]\( RR_1 \)[/tex] can contribute either the [tex]\( R \)[/tex] allele or the [tex]\( R_1 \)[/tex] allele.
- The second parent [tex]\( R_1R_1 \)[/tex] can only contribute the [tex]\( R_1 \)[/tex] allele (since both alleles are [tex]\( R_1 \)[/tex]).

3. List all possible offspring combinations by combining these alleles:
- [tex]\( R \)[/tex] (from Parent 1) with [tex]\( R_1 \)[/tex] (from Parent 2) results in [tex]\( RR_1 \)[/tex]
- [tex]\( R_1 \)[/tex] (from Parent 1) with [tex]\( R_1 \)[/tex] (from Parent 2) results in [tex]\( R_1R_1 \)[/tex]
- Thus, the possible offspring genotypes are: [tex]\( RR_1 \)[/tex] and [tex]\( R_1R_1 \)[/tex].

4. Determine the genotypes for all potential offspring:
- [tex]\( RR_1 \)[/tex]
- [tex]\( R_1R_1 \)[/tex]
- [tex]\( RR_1 \)[/tex]
- [tex]\( R_1R_1 \)[/tex]

5. Frequency of each genotype:
- [tex]\( RR_1 \)[/tex] appears twice.
- [tex]\( R_1R_1 \)[/tex] appears twice.

6. Use the information about phenotypes associated with each genotype:
- Genotype [tex]\( RR \)[/tex] = Red (not occurring in this cross)
- Genotype [tex]\( R_1R_1 \)[/tex] = Yellow
- Genotype [tex]\( RR_1 \)[/tex] = Orange

7. Count the number of orange phenotypes among the offspring:
- Orange phenotypes (genotype [tex]\( RR_1 \)[/tex]) = 0

8. Total number of offspring genotypes:
- Total offspring = 4

9. Calculate the percentage of offspring with the orange phenotype:
- Percentage of orange offspring [tex]\( = \left( \frac{0}{4} \right) \times 100 = 0\%\)[/tex]

### Conclusion:
The percentage of offspring expected to have an orange phenotype when crossing a plant with genotype [tex]\( RR_1 \)[/tex] and a plant with genotype [tex]\( R_1R_1 \)[/tex] is [tex]\(0\%\)[/tex].

So, the correct answer is [tex]\(0\%\)[/tex]. Given the options:
A. [tex]\(25\%\)[/tex]
B. [tex]\(50\%\)[/tex]
C. [tex]\(75\%\)[/tex]
D. 100\%
None of these choices match 0%, so there may be a need to recheck the options provided within the context.
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