Every phenotype (characteristic or trait) has a corresponding genotype (a combination of alleles from the father and mother). Some combinations of alleles lead to the expression of one allele over the other. Dominant alleles are expressed when they combine with dominant or recessive alleles. A recessive allele gets expressed in an individual only when it combines with another recessive allele to create a homozygous recessive chromosome. Click each trait in the table below to see its corresponding genotype.
| Trait or Character | Phenotype | Genotype |
| hairline | widow's peak (A), straight (a) | AA homozygous dominant, Aa heterozygous dominant, aa homozygous recessive |
| earlobe | free hanging (A), attached (a) | AA homozygous dominant, Aa heterozygous dominant, aa homozygous recessive |
| flower color | Purple (A), white (a) | AA homozygous dominant, Aa heterozygous dominant, aa homozygous recessive |
| height | tall (T), short (t) | TT homozygous dominant, Tt heterozygous dominant, tt homozygous recessive |
Question
Can we accurately tell the specific genotype of a tall tree just by looking at it?
No, but we can make some predictions. For example, a tall tree must either have a homozygous (TT) dominant genotype or a heterozygous (Tt) dominant genotype.
