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Petunia flower color is governed by two alleles, but neither allele is truly dominant over the other. Petunias with the genotype R1 R1 are red-flowered, those that are heterozygous (R1 R2 ) are pink, and those with the R2 R2 genotype are white. This is an example of incomplete dominance. (Note that superscripts are used rather than upper- and lowercase letters to describe the alleles).
a. If a white-flowered plant is crossed with a red-flowered plant, what is the genotypic ratio of the F1?b. What is the phenotypic ratio of the F1?c. If two of the F1 offspring were crossed, what phenotypes would appear in the F2?d. What would be the genotypic ratio in the F2 generation?

Sagot :

Samueladesida43idn

Answer:

a. 4 R¹R²

b. 4 Pink flowers

c. 1 Red, 2 pink and 1 white phenotypes

d. 1R¹R¹ : 2R¹R² : 1R²R²

Explanation:

This question involves a single gene coding for flower color in petunia plants. However, the allele for red flower color (R¹) is incompletely dominant over the allele for white flower color (R²), hence, a pink intermediate phenotype (R¹R²) is formed.

According to these questions;

A. If a white-flowered plant (R²R²) is crossed with a red-flowered plant (R¹R¹), all of the F1 generation will have a genotype of R¹R² (see attached image for punnet square).

B. The F1 generation, which possess a genotype: R¹R² will express the pink flower phenotype because neither of the two alleles are truly dominant over the other i.e incomplete dominance.

C. If two of the F1 offspring were crossed i.e. R¹R² × R¹R², each parent will produce R¹ and R² gametes. Using these gametes in a punnet square (see attached image), the following phenotypes will be produced in the F2 generation: Red, pink and white phenotypes

D. The F2 generation will possess a genotypic ratio of 1R¹R¹ : 2R¹R² : 1R²R².

View image Samueladesida43
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