Suppose a dominant allele (N) codes for a big nose and a recessive allele (n) codes for a small nose. Imagine that an organism receives a dominant allele from its mom and a dominant from its dad. What can be determined about its genotype and phenotype?

From the information given, we can determine that the organism's genotype is:

Nn (heterozygous dominant, aka one dominant allele and one recessive one)

Phenotype refers to how the genotype manifests in the organism, and since a dominant allele overrides the recessive one, the phenotype must be 'Big Nose' for this organism.