* Recessive alleles: If an individual carries two copies of a recessive allele, they will express the trait associated with that allele. However, if they only carry one copy of the recessive allele and one copy of the dominant allele, they will not express the trait. They are carriers of the recessive allele, meaning they can pass it on to their offspring.
* Incomplete dominance: In some cases, neither allele is completely dominant over the other. Instead, the heterozygous individual exhibits a phenotype that is a blend of the two homozygous phenotypes. This can be observed in snapdragon flower color, where a red flower crossed with a white flower produces pink offspring.
* Codominance: In codominance, both alleles are expressed equally in the heterozygous individual. For example, in blood type AB, both the A and B alleles are expressed, resulting in a phenotype that is distinct from either homozygous genotype.
* Epistasis: This occurs when the expression of one gene masks the expression of another gene. For example, in Labrador retrievers, the gene for coat color (black or brown) is epistatic to the gene for coat pigment (presence or absence of pigment). A dog with two copies of the recessive "e" allele at the pigment locus will be yellow regardless of its genotype at the coat color locus.
* Silent mutations: These mutations do not change the amino acid sequence of a protein. Therefore, they do not affect the phenotype.
* Non-coding DNA: A significant portion of the genome is non-coding DNA. This DNA does not contain instructions for building proteins and does not directly contribute to the phenotype.
It is important to note that even if a gene is not expressed in a phenotype, it can still be present in the individual's genome and can be passed on to their offspring.
