Well actually not necessarily. An individual can be homozygous or heterozygous dominant for a trait. As long as they have that dominant allele in that specific genetic trait, they will automatically express the dominant phenotype. If a person is homozygous dominant, it just means that they will pass on both dominant traits to the offspring. If a person is heterozygous dominant , it means that they will pass on both a dominant and recessive trait to their offspring.
Hope that helps ! =D
To determine the genotype of an individual that shows the dominant phenotype you would cross that individual with one that is homozygous recessive. A monohybrid cross of two individuals that are heterozygous for a trait exhibiting complete dominance would probably result in a phenotype ratio is 3 dominant 1 recessive.
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.
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.
There is dominant and there is recessive. There is no dominant recessive. A dominant gene will always be expressed when present, such as in the homozygous dominant genotype (RR), or heterozygous genotype (Rr). A recessive allele is only expressed when the genotype is homozygous recessive (rr).
When the dominant and recessive traits are known, using the term "homozygous" for the recessive phenotype is redundant because it implies that both alleles are the same (rr for a recessive phenotype). It is clear that the individual is homozygous for the recessive allele by observing their phenotype.
100 percent.
Given those conditions, the offspring have a 50% chance of demonstrating the dominant phenotype and a 50% chance of demonstrating the recessive phenotype.
To determine the genotype of an individual that shows the dominant phenotype you would cross that individual with one that is homozygous recessive. A monohybrid cross of two individuals that are heterozygous for a trait exhibiting complete dominance would probably result in a phenotype ratio is 3 dominant 1 recessive.
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.
The homozygous dominant individual can only pass on the dominant allele and the homozygous recessive individual can only pass on the recessive allele, therefore all offspring will be heterozygous and have the dominant phenotype.
A recessive allele for a trait is expressed in the phenotype of an individual only when the individual is homozygous for that allele, meaning it has two copies of the recessive allele (one from each parent). If the individual has at least one dominant allele for that trait, the dominant trait will be expressed instead. Therefore, the presence of the recessive phenotype is only visible when both alleles are recessive.
In a test cross, one individual with a dominant phenotype but unknown genotype is crossed with a homozygous recessive individual. The genotype of the individual with the dominant phenotype can then be inferred based on the phenotypic ratios of the offspring.
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.
In a testcross, an individual with a dominant phenotype but unknown genotype is crossed with an individual that is homozygous recessive for the same trait. This helps determine the unknown genotype of the dominant individual based on the phenotypic ratios of the offspring. If any offspring display the recessive phenotype, it indicates that the dominant parent is heterozygous. Conversely, if all offspring show the dominant phenotype, the dominant parent is likely homozygous.
testcross
Homozygous recessive.
Dominant alleles are expressed when an individual has at least one copy of the dominant allele in their genotype. This means that even if there is a recessive allele present, the dominant allele will be the one observed in the phenotype. Dominant alleles mask the expression of recessive alleles when they are both present in an individual's genetic makeup.