In a unique species of plants, flowers may be yellow, blue, red, or mauve. All colors may be true breeding, If plants with blue flowers are crossed to red- flowered plants, all \(\mathrm{F}_{1}\) plants have yellow flowers. When these produced an \(\mathrm{F}_{2}\) generation, the following ratio was observed: \(9 / 16\) yellow: \(3 / 16\) blue: \(3 / 16\) red: \(1 / 16\) mauve In still another cross using true-breeding parents, yellow-flowered plants are crossed with mauve-flowered plants. Again, all \(\mathrm{F}_{1}\) plants had yellow flowers and the \(\mathrm{F}_{2}\) showed a 9: 3: 3: 1 ratio, as just shown. (a) Describe the inheritance of flower color by defining gene symbols and designating which genotypes give rise to cach of the four phenotypes. (b) Determine the \(F_{1}\) and \(F_{2}\) results of a cross between truebreeding red and true-breeding mauve-flowered plants.

Step by step solution

01

Analyze the given information

We are given the following information: - When blue-flowered plants are crossed with red-flowered plants, all F1 plants have yellow flowers. - In the F2 generation, the ratio is 9/16 yellow, 3/16 blue, 3/16 red, 1/16 mauve. - When yellow-flowered plants are crossed with mauve-flowered plants, all F1 plants have yellow flowers. - In the F2 generation, the ratio is 9:3:3:1 (yellow:blue:red:mauve). From this information, we can infer that the inheritance of flower color follows a dihybrid inheritance pattern since we observe a 9:3:3:1 ratio in the F2 generation.

02

Define gene symbols

We will use the capital letter Y for the dominant yellow allele and y for the recessive mauve allele. Similarly, we will use the capital letter R for the dominant-red allele and r for the recessive blue allele.

03

Determine genotypes of the four phenotypes

Based on the information given and the gene symbols we have defined, the genotypes for each flower color are as follows: - Yellow: \(YYRR, YYRr, YyRR,\) or \(YyRr\) - Blue: \(YYrr\) - Red: \(Yyrr\) - Mauve: \(Yyrr\)

04

Predict the F1 and F2 generation results for a cross between true-breeding red and true-breeding mauve-flowered plants

True-breeding red plants have the genotype \(Yyrr\) and true-breeding mauve plants have the genotype \(yyrr\). We will now cross these plants and evaluate the F1 and F2 generation results. (a) F1 generation: Parents: \(Yyrr \times yyrr\) Offspring: All the F1 offspring will have the genotype \(Yyrr\). Therefore, all the F1 generation plants will have red flowers. (b) F2 generation: To predict the F2 generation, we will perform a self-cross between two F1 generation plants. So, the cross will be: Parents: \(Yyrr \times Yyrr\) We can use a Punnett square to determine the resulting F2 genotypes and phenotypes: 1. \(YYRR\) (yellow) - \(1/16\) 2. \(YYRr\) (yellow) - \(2/16\) 3. \(YyRR\) (yellow) - \(2/16\) 4. \(YyRr\) (yellow) - \(4/16\) 5. \(YYrr\) (blue) - \(1/16\) 6. \(Yyrr\) (red) - \(4/16\) 7. \(yyrr\) (mauve) - \(1/16\) As a result, in the F2 generation, we observe a 9:1:4:1 ratio (yellow:blue:red:mauve).

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