It depends on what you mean by "both are expressed".
In order for both alleles to be expressed, both alleles must be dominant alleles. If one allele is recessive, it will be masked.
If you are talking about alleles that are co-dominant, then both alleles would be expressed together. Ex: Red x white = red and white flower
If you are talking about incomplete dominance, then both alleles are seen as a blend of both in the offspring. Ex: red x white = pink flower
If you are talking about multiple alleles (like in human blood typing), then you can see 2 alleles expressed together. Ex: Type A x Type B can produce AB blood type.
In order for both traits to be expressed the two alleles of the heterozygote must be co-dominant. It is also dependent on whether the partner is homozygous or heterozygous for the same trait.
So to answer the question there is no real pattern for co-dominance unless the partner's genetics are known. Co-dominance is what makes cows black and white and makes flowers with pink petals (co-dominance of the white and red allele).
The variations based on each possible partner are too complicated to get into. A more specific question would be good.
Polygenic inheritance is an inheritance pattern in which a trait is controlled by multiple genes, each with two or more alleles. This results in a continuous range of phenotypes rather than distinct categories.
Both co-dominance and incomplete dominance involve a situation where alleles do not follow the traditional dominant-recessive pattern of inheritance. In both cases, heterozygous individuals show a phenotype that is a blend of the two homozygous phenotypes. The main difference is that in co-dominance, both alleles are fully expressed, while in incomplete dominance, the phenotype is a mix of the two alleles.
Codominance is a genetic concept where two different alleles for a gene are both expressed in the phenotype of a heterozygous individual. This results in a phenotype that shows traits from both alleles rather than a blending of the two.
Codominance is an inheritable pattern where two different alleles for a gene are both expressed in the phenotype, resulting in a unique trait that displays characteristics of both alleles. This leads to a distinct phenotype that is a combination of the traits produced by both alleles.
No, the determination of whether an allele is dominant or recessive is based on the inheritance pattern of the traits. Dominant alleles are expressed in the phenotype even if only one copy is present, while recessive alleles are only expressed when two copies are present. Phenotype ratios in a population can hint at the presence of dominant or recessive traits but do not definitively determine the dominance relationship of an allele.
Types of dominance, multiple alleles, sex linked inheritance, polygenic inheritance and maternal inheritance.
Codominance is the pattern of inheritance in which both alleles contribute to the phenotype of the organism. This means that neither allele is dominant or recessive, and both are expressed in the phenotype of the individual.
codominant alleles
Polygenic inheritance is an inheritance pattern in which a trait is controlled by multiple genes, each with two or more alleles. This results in a continuous range of phenotypes rather than distinct categories.
codominace
No, recessive traits refer to the inheritance pattern of the allele. In the simple case where a trait is either expressed or not, if it is a recessive trait it will only be the expressed phenotype when it is homozygous. Dominant allele phenotypes will show if the genotype is heterozygous.
Incomplete dominance
When a trait has more than two alleles, it can be inherited in various ways depending on the interaction of the alleles. Multiple alleles can exist at a single genetic locus, and the specific inheritance pattern is determined by factors like dominance, recessiveness, and co-dominance. Each individual can still only inherit two alleles for a specific gene, but the presence of multiple alleles can create a wider range of possible genotypes and phenotypes.
Both co-dominance and incomplete dominance involve a situation where alleles do not follow the traditional dominant-recessive pattern of inheritance. In both cases, heterozygous individuals show a phenotype that is a blend of the two homozygous phenotypes. The main difference is that in co-dominance, both alleles are fully expressed, while in incomplete dominance, the phenotype is a mix of the two alleles.
Mendel proposed the concept of dominant and recessive alleles that determine trait expression in offspring. Through his experiments, he discovered that traits can disappear in one generation due to being masked by dominant alleles, but can reappear in future generations when those recessive alleles are passed down and expressed. This pattern of inheritance is now known as Mendelian genetics.
Codominance is a genetic concept where two different alleles for a gene are both expressed in the phenotype of a heterozygous individual. This results in a phenotype that shows traits from both alleles rather than a blending of the two.
A pattern where both versions, or alleles, of a gene are fully expressed in the phenotype is called codominance. In this scenario, the traits associated with both alleles are visible in the offspring. An example is the ABO blood group system, where an individual can have both A and B antigens expressed on their red blood cells if they inherit both A and B alleles.