Final answer:
The phenotype produced by a pair of Rr alleles is determined by the dominance of the alleles, where the dominant allele typically dictates the phenotype completely, but in the case of incomplete dominance or co-dominance, a blended or unique phenotype may result.
Step-by-step explanation:
The phenotype produced from a pair of alleles Rr is determined by the dominance of the alleles. In genetics, traits are expressed through the interaction between alleles, which are different forms of a gene. When there is a pair of heterozygous alleles, such as Rr, where 'R' represents the dominant allele and 'r' represents the recessive allele, the phenotype is typically determined by the dominant allele.
In cases where the dominance is complete, the dominant phenotype will be expressed, making the probability of expressing the dominant phenotype 100 percent. However, in some situations like incomplete dominance or co-dominance, both alleles can contribute to the phenotype, resulting in a blended or unique phenotype respectively. An example of incomplete dominance is when a plant that is homozygous for the red allele (RR) is crossed with a plant that is homozygous for the white allele (WW), producing offspring with pink flowers (RW) where neither allele is completely dominant.