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).

A cross of two geraniums yields offspring that are 100% Rr.

Which choice best represents the alleles of the parents?

A. RR and rr
B. Rr and rr
C. RR and Rr
D. Rr and Rr

The likely parental genotypes for a 100% Rr progeny would be RR and rr. Each parent contributes one allele during fertilization, thus resulting in all offspring carrying the Rr genotype.

Explanation:

The horticulturalist wants to produce geraniums with specific characteristics, so the alleles of the parents can be inferred from the outcome of the cross, which states that they yield 100% Rr offspring. In this case, it would mean each parent must have had one R and one r allele to pass on to ensure that all offspring were Rr. Therefore, the best representation of the parents' alleles would be RR and rr.

Here's an illustration: Each parent produces gametes (reproductive cells) that have only one copy of each gene, represented by one allele. The RR parent would only have R alleles to pass on, and similarly, the rr parent would only have r alleles to contribute to the offspring. The fertilization event, merging these gametes together, would result in offspring that are all Rr, possessing one allele from each parent.

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