The AA genotype typically produces the phenotype associated with the dominant allele A. This means that the dominant trait will be expressed in the individual with this genotype.
If AA represents a dominant widow's peak trait, a child born without a widow's peak would have the recessive phenotype, which is aa. So the child would not have a widow's peak.
An Aa genotype can result in the same phenotype as either an AA or AA genotype, if one of the alleles acts in a dominant fashion. If the A allele is dominant over the a allele, then the phenotype of a heterozygous (Aa) individual will be the same as the phenotype of a homozygous dominant (AA) individual.
Genotype: AA - The phenotype is homozygous dominant, exhibiting the dominant trait. Genotype: Aa - The phenotype is heterozygous, exhibiting the dominant trait. Genotype: aa - The phenotype is homozygous recessive, exhibiting the recessive trait.
B.
If two alleles are dominant, the phenotypes will reflect the dominant traits associated with each allele. Both alleles will be expressed in the phenotype, resulting in a phenotype that shows the dominant characteristics of both alleles.
Homozygous dominant genotype (AA): The phenotype will show the dominant trait. Heterozygous genotype (Aa): The phenotype will also show the dominant trait due to the presence of at least one dominant allele. Homozygous recessive genotype (aa): The phenotype will exhibit the recessive trait.
If one parent is homozygous dominant (AA) and the other parent is homozygous recessive (aa), all offspring will inherit one dominant allele and display the dominant phenotype. Therefore, the probability of their offspring exhibiting the dominant phenotype is 100%.
AA (dominant) mating with aa (recessive) -----> Aa
The genotype would need to have at least one copy of the dominant allele. For example, in a simple Mendelian trait where dominant allele is represented by "A" and the recessive allele by "a", the genotype could be either "AA" or "Aa" to result in a dominant phenotype.
Purebreds can be recessive or dominant, depending on their genotype. A genotype for spots on a griaffe could be AA (purebred dominant), Aa (heterozygous dominant), or AA (purebred recessive)? AA and Aa would both show the dominant phenotype, but only AA and AA are purebreds.
From the cross Aa x Aa, the probability of producing a homozygous dominant offspring is 1/4 or (0.25).