Answer :
The correct answer is option- C. The unknown geranium is heterozygous for red flowers (Rr).
As per the scenario given in the question, half of the plants have red flowers and half have white flowers after crossing a red geranium of uncertain genetic makeup with a white geranium (rr), implies that the genetic makeup of the red geranium parent was heterozygous for red flowers (Rr). If the red geranium had been homozygous for red flowers (RR), all offspring would have had red flowers. The presence of white flowers in the offspring rules out the possibility of the red geranium being homozygous for red, hence the conclusion is that it carries one allele for red flowers and one for white flowers (Rr).
Complete question:
A horticulturalist wants to produce geraniums with specific characteristics. She knows that the trait of red flowers is governed by the allele R (RR and Rr) and the trait of white flowers is governed by the allele r (rr).
The horticulturalist has a red geranium with an uncertain genetic makeup. She crosses it with a white geranium (rr) and gets a generation in which half of the plants have red flowers and half have white flowers. What does this combination of offspring tell her about the genetic makeup of the red geranium parent?
A) The trait shows incomplete dominance.
B) The unknown geranium is homozygous for white flowers (rr).
C) The unknown geranium is heterozygous for red flowers (Rr).
D) The unknown geranium is homologous for red flowers (RR).
The combination of red and white flowers in the offspring indicates that the unknown geranium's genotype is heterozygous for red flowers (Rr), with incomplete dominance being the pattern of inheritance.
When the horticulturalist crosses an unknown geranium with a red geranium (rr) and gets an equal number of red and white flowers among the offspring, it tells us about the genetic makeup of the unknown geranium parent. Since half of the plants have red flowers and half have white flowers, the unknown geranium must be heterozygous for red flowers (Rr). This outcome suggests incomplete dominance in geranium flower color phenotypes, an inheritance pattern where neither allele is completely dominant, and heterozygotes express an intermediate phenotype. In this scenario, the red allele is incompletely dominant over the white allele, giving rise to red and white flower colors when the unknown geranium's genotype is heterozygous.
