C = dominant c = recessive (cystic fibrosis) CC, cc = homozygous (homo = same) Cc = heterozygous (hetero = different) Recessive traits are expressed only when two recessive alleles are present If you get <em>CC</em>, you will not have cystic fibrosis. (<em>c </em>is the cystic fibrosis allele) This person would be homozygous dominant and would not pass on the disease because they do not have any cystic fibrosis alleles. If you get<em> Cc</em> you will not have cystic fibrosis b/c the<em> C</em> is dominant and overrides the cystic fibrosis allele <em>c</em>. This person would be heterozygous and, though they do not have the disease, they would still have a chance of passing on the disease because they carry the cystic fibrosis allele.
If you get <em>cc</em> you will have cystic fibrosis b/c <em>c</em> is the cystic fibrosis allele and it is not being overridden by a dominant allele. This person would be homozygous recessive.<em />