Question

If an organism expresses a recessive phenotype, can you tell the genotype?

Answer 1

Yes. Since a recessive phenotype would need both recessive alleles, you could tell that the alleles are both lower case

For example, if we have BB, Bb, bB, and bb...

BB, Bb, bB would all be dominant.

bb, on the otherhand, would be recessive -- it is the only combination that would show a recessive phenotype.