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In Mirabilis plant, tallness is complete...

In Mirabilis plant, tallness is completely dominant over dwarfness, while red flower exhibit incomplete dominance over white flower. If tall and pink flowered plant, on selfing shows 1:2:1 phenotypic ratio then what would be genotype of the plants?

A

TRr

B

TTRR

C

TTRR

D

TTRr

Text Solution

AI Generated Solution

The correct Answer is:
To determine the genotype of the Mirabilis plant that exhibits tallness and pink flowers, we can follow these steps: ### Step 1: Understand the Traits - **Tallness (T)** is completely dominant over **dwarfness (t)**. - **Flower color** exhibits incomplete dominance, where: - **Red (R)** is dominant over **white (r)**, leading to pink (Rr) when mixed. ### Step 2: Analyze the Given Information - The plant in question is tall and has pink flowers. - The phenotypic ratio from selfing this plant is 1:2:1. ### Step 3: Determine the Genotypes Since the phenotypic ratio is 1:2:1, it suggests a dihybrid cross involving two traits (height and flower color). The possible genotypes for the tall and pink flowered plant can be: - For height (T): - TT (homozygous tall) - Tt (heterozygous tall) - For flower color (R): - RR (homozygous red) - Rr (heterozygous pink) - rr (homozygous white) ### Step 4: Identify the Possible Combinations Given that the plant is tall and has pink flowers, the possible genotypes are: - TTRr (homozygous tall, heterozygous pink) - TtRr (heterozygous tall, heterozygous pink) ### Step 5: Perform the Selfing 1. **If the genotype is TTRr:** - Gametes produced: TR, Tr (2 types) - Offspring: - 1 TTRR (tall red) - 2 TTRr (tall pink) - 1 TTRr (tall pink) - 1 TTRr (tall pink) - 1 TtRR (tall red) - 2 TtRr (tall pink) - 1 Ttrr (tall white) - Phenotypic ratio: 1 tall red: 2 tall pink: 1 tall white 2. **If the genotype is TtRr:** - Gametes produced: TR, Tr, tR, tr (4 types) - Offspring: - 1 TTRR (tall red) - 2 TTRr (tall pink) - 1 TTRr (tall pink) - 1 TtRR (tall red) - 2 TtRr (tall pink) - 1 Ttrr (tall white) - Phenotypic ratio: 1 tall red: 2 tall pink: 1 tall white ### Conclusion The observed 1:2:1 phenotypic ratio indicates that the genotype of the tall and pink flowered plant is **TtRr**. ### Final Answer The genotype of the plants is **TtRr**. ---
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