Praxis 5005 Practice Test Practice Question
In a species of flowering plant, red flower color is dominant to white flower color, where R is the dominant allele and r is the recessive allele. What is the expected phenotypic ratio of the offspring from the cross Rr × Rr
Correct Answer: A
Rationale: In a cross between two heterozygous red-flowered plants (Rr × Rr), the expected genotypic ratio is 1 RR : 2 Rr : 1 rr. This results in a phenotypic ratio of 3 red-flowered plants (RR and Rr) to 1 white-flowered plant (rr), confirming option A.
Option B suggests an incorrect ratio, reversing the expected outcomes. Option C indicates that all offspring would be white-flowered, which is impossible given the dominance of the red allele. Option D states all offspring would be red-flowered, overlooking the presence of the recessive homozygous genotype. Thus, option A accurately reflects the genetic principles at play.
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