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Sagot :
Absolutely! Let's analyze the given problem step by step.
The table you provided represents the offspring from a cross between round-seeded peas (dominated by the allele [tex]\(R\)[/tex]) and wrinkle-seeded peas (dominated by the allele [tex]\(r\)[/tex]). The table shows the following genotypes:
[tex]\[ \begin{array}{|c|c|c|} \hline & R & r \\ \hline R & RR & Rr \\ \hline R & Rr & rr \\ \hline \end{array} \][/tex]
Let's address each part of the question.
### i. What is the ratio of plants showing dominant and recessive characters?
Dominant characters are exhibited by plants with at least one dominant allele [tex]\(R\)[/tex]. The genotypes [tex]\(RR\)[/tex] and [tex]\(Rr\)[/tex] show dominant characters (round seeds).
Recessive characters are shown by plants with two recessive alleles [tex]\(rr\)[/tex] (wrinkled seeds).
From the table, we can count:
- [tex]\(RR\)[/tex] (1 occurrence)
- [tex]\(Rr\)[/tex] (2 occurrences)
- [tex]\(rr\)[/tex] (1 occurrence)
Thus, the ratio of plants showing dominant (round) to recessive (wrinkled) characters is:
[tex]\[ \text{Dominant:Recessive} = 3:1 \][/tex]
### ii. Write the genotypic and phenotypic ratio of this generation.
The genotypic ratios are derived from the individual genotypes present in the table:
- [tex]\(\text{RR}\)[/tex] for pure round seeds: 1 occurrence
- [tex]\(\text{Rr}\)[/tex] for hybrid round seeds: 2 occurrences
- [tex]\(\text{rr}\)[/tex] for pure wrinkled seeds: 1 occurrence
Thus, the genotypic ratio is:
[tex]\[ \text{Genotypic Ratio} = \{ \text{RR: 1}, \text{Rr: 2}, \text{rr: 1} \} \][/tex]
The phenotypic ratios are derived from the appearance (or traits) of the seeds:
- Round seeds (either [tex]\(RR\)[/tex] or [tex]\(Rr\)[/tex]): 3 occurrences
- Wrinkled seeds ([tex]\(rr\)[/tex]): 1 occurrence
Thus, the phenotypic ratio is:
[tex]\[ \text{Phenotypic Ratio} = \{ \text{Round: 3}, \text{Wrinkled: 1} \} \][/tex]
### iii. Among them, which plant is purely round-seeded? Why?
A plant is considered purely round-seeded if it has the genotype consisting of two dominant alleles [tex]\(RR\)[/tex]. This is because [tex]\(RR\)[/tex] means the plant has inherited the dominant round seed trait from both parents.
So, the purely round-seeded plant is:
[tex]\[ \text{Genotype} = \text{RR} \][/tex]
This genotype ensures the plant is purely round-seeded, as it does not carry the recessive allele [tex]\(r\)[/tex].
### Summary:
1. The ratio of plants showing dominant to recessive characters is 3:1.
2. The genotypic ratio of this generation is \{RR: 1, Rr: 2, rr: 1\} and the phenotypic ratio is \{Round: 3, Wrinkled: 1\}.
3. The purely round-seeded plant has the genotype [tex]\(RR\)[/tex] because it contains two dominant alleles without any recessive allele.
The table you provided represents the offspring from a cross between round-seeded peas (dominated by the allele [tex]\(R\)[/tex]) and wrinkle-seeded peas (dominated by the allele [tex]\(r\)[/tex]). The table shows the following genotypes:
[tex]\[ \begin{array}{|c|c|c|} \hline & R & r \\ \hline R & RR & Rr \\ \hline R & Rr & rr \\ \hline \end{array} \][/tex]
Let's address each part of the question.
### i. What is the ratio of plants showing dominant and recessive characters?
Dominant characters are exhibited by plants with at least one dominant allele [tex]\(R\)[/tex]. The genotypes [tex]\(RR\)[/tex] and [tex]\(Rr\)[/tex] show dominant characters (round seeds).
Recessive characters are shown by plants with two recessive alleles [tex]\(rr\)[/tex] (wrinkled seeds).
From the table, we can count:
- [tex]\(RR\)[/tex] (1 occurrence)
- [tex]\(Rr\)[/tex] (2 occurrences)
- [tex]\(rr\)[/tex] (1 occurrence)
Thus, the ratio of plants showing dominant (round) to recessive (wrinkled) characters is:
[tex]\[ \text{Dominant:Recessive} = 3:1 \][/tex]
### ii. Write the genotypic and phenotypic ratio of this generation.
The genotypic ratios are derived from the individual genotypes present in the table:
- [tex]\(\text{RR}\)[/tex] for pure round seeds: 1 occurrence
- [tex]\(\text{Rr}\)[/tex] for hybrid round seeds: 2 occurrences
- [tex]\(\text{rr}\)[/tex] for pure wrinkled seeds: 1 occurrence
Thus, the genotypic ratio is:
[tex]\[ \text{Genotypic Ratio} = \{ \text{RR: 1}, \text{Rr: 2}, \text{rr: 1} \} \][/tex]
The phenotypic ratios are derived from the appearance (or traits) of the seeds:
- Round seeds (either [tex]\(RR\)[/tex] or [tex]\(Rr\)[/tex]): 3 occurrences
- Wrinkled seeds ([tex]\(rr\)[/tex]): 1 occurrence
Thus, the phenotypic ratio is:
[tex]\[ \text{Phenotypic Ratio} = \{ \text{Round: 3}, \text{Wrinkled: 1} \} \][/tex]
### iii. Among them, which plant is purely round-seeded? Why?
A plant is considered purely round-seeded if it has the genotype consisting of two dominant alleles [tex]\(RR\)[/tex]. This is because [tex]\(RR\)[/tex] means the plant has inherited the dominant round seed trait from both parents.
So, the purely round-seeded plant is:
[tex]\[ \text{Genotype} = \text{RR} \][/tex]
This genotype ensures the plant is purely round-seeded, as it does not carry the recessive allele [tex]\(r\)[/tex].
### Summary:
1. The ratio of plants showing dominant to recessive characters is 3:1.
2. The genotypic ratio of this generation is \{RR: 1, Rr: 2, rr: 1\} and the phenotypic ratio is \{Round: 3, Wrinkled: 1\}.
3. The purely round-seeded plant has the genotype [tex]\(RR\)[/tex] because it contains two dominant alleles without any recessive allele.
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