Question

5.   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 allele from its dad. What can be determined about its genotype and phenotype?

A. The organism has a large nose, because it's homozygous.
  B. The organism has a large nose, because it's heterozygous.
  C. The organism has a small nose, because it's heterozygous.
  D. The organism has a small nose, because it's homozygous.

Answer 1

A. The organism has a large nose, because it's homozygous.

If the organism got from its mom a dominant allele, and from its dad a dominant allele also, the organism will be homozygous dominant. The dominant characteristic is a large nose, therefore the organism will have a large nose as he is homozygous dominant for that trait. If he was heterozygous, he would still have a large nose because it is the dominant trait. To have a small nose, the organism would have to receive from its parents, two recessive alleles.