Yes, both Aa and AA genotypes represent the dominant phenotype for a specific trait. The presence of at least one dominant allele (A) will result in the dominant phenotype being expressed.
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.
When you cross two F1 individuals (both being heterozygous for a trait, for example, Aa), the expected genotype ratio in the F2 generation would be 1 AA : 2 Aa : 1 aa. The phenotype ratio, assuming A is dominant over a, would typically be 3 dominant phenotype (AA and Aa) to 1 recessive phenotype (aa). Therefore, you would expect three individuals displaying the dominant trait for every one individual displaying the recessive trait in the F2 generation.
The Phenotype would be a straight hairline. The genotype would be aa.
If you cross a homozygous dominant individual (AA) with a heterozygous individual (Aa), the offspring will have a genotype ratio of 100% dominant phenotype (AA or Aa) and 0% recessive phenotype (aa). Therefore, if your offspring has a homozygous dominant trait (AA), the likelihood of expressing a recessive trait (aa) is 0%. The Punnett square for this cross would show all dominant traits, confirming that recessive traits cannot be expressed in this scenario.
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.
For a single gene trait with two alleles, one dominant and one recessive, there are three possible genotypes: homozygous dominant (AA), heterozygous (Aa), and homozygous recessive (aa). In terms of phenotypes, there are typically two: the dominant phenotype (AA and Aa) and the recessive phenotype (aa). Thus, there are three genotypes and two phenotypes for this trait in the population.
To determine the phenotype ratio of a cross between a heterozygous male (let's say genotype Aa for a trait with A being dominant and a being recessive) and a pink-eyed female (assumed to be homozygous recessive aa), you would set up a Punnett square. The resulting offspring genotypes would be Aa (dominant phenotype) and aa (recessive phenotype). The phenotype ratio would be 1:1, with 50% showing the dominant phenotype and 50% showing the recessive phenotype.
B.
When a homozygous dominant female (genotype AA) is crossed with a homozygous recessive male (genotype aa), all offspring will inherit one dominant allele from the mother and one recessive allele from the father, resulting in a genotype of Aa for all offspring. The phenotype ratio will show all offspring displaying the dominant trait. Thus, the genotype ratio is 100% Aa, and the phenotype ratio is 100% expressing the dominant trait.
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.