Question

At the end of your biology class, your professor asks you to develop a project to determine the genotype of a plant with red flowers. Red petal color (R) is dominant to pink flower color (r). To accomplish this task, you cross the plant with the unknown genotype with heterozygous red-flowered plants. Which of the following are valid predictions of the ratio of flower colors in the offspring? partially filled Punnett square is provided.

Answer 1

The question lacks options and the incomplete punnet square; the incomplete punnet square has been added as an attachment while these are the options:

A) All red flowers

B) All pink flowers

C) 1 red : 3 pink flowers

D) 3 red : 1 pink flowers

The answer is D

Step-by-step explanation:

According to the question, the genotype of a plant that produces red flower phenotype is about to be determined. For this flower colour gene, two alleles are involved in which the red color (R) allele is dominant over the pink color (r) allele I.e. the R allele will mask the expression of r allele in a heterozygous state.

The red-flowered plant with unknown genotype was crossed with a heterozygous red-flowered plant (Rr). Since a red flowered plant can either be Rr (heterozygous) or RR (homozygous), we use the Rr plant in the punnet square. The unknown genotype, assuming it has a Rr genotype, will produce RR, Rr, Rr and rr offsprings when crossed with another heterozygote (Rr).

These offsprings show a 3 red : 1 pink phenotypic ratio, making option D a valid prediction.

R r

R RR Rr

r Rr rr