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The alleles are not always both expressed.
Take the simplest example, a case when there are only two alleles for a trait, R and r. When the organism is a heterozygote, meaning that it has both alleles with a genotype of Rr, only the phenotype carried by the dominant allele, the R, will be expressed. The dominant allele masks the phenotype of the recessive allele. A case in which only the dominant phenotype is expressed in a heterozygote is a case of complete dominance.
*Cases where the dominant allele does not completely mask the recessive allele are cases of incomplete dominance and co-dominance.
In incomplete dominance, the dominant allele has some effect on the recessive allele, but not a full effect. This results in a third phenotype in the population. Think red and white flowers leading to pink flowers.
In co-dominance, the dominant allele has as much effect on the phenotype of the organism as the recessive allele. Think red and white flowers now leading to red and white streaked flowers.
In most cases, only one allele is expressed per gene due to dominance and recessiveness. However, in cases of codominance or incomplete dominance, both alleles can be expressed simultaneously, leading to a blending or combined phenotype. This is observed in traits such as blood type in humans (AB blood type from A and B alleles) or flower color in snapdragons.
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A recessive allele is represented by an letter?
In genetics, a recessive allele is typically represented by a lowercase letter. For example, if the dominant allele is represented by "A", the recessive allele for the same trait would be represented by "a".
What is it called when two forms of trait are both dominant at the same time?
Codominance. It's the case of AB blood types, for instance. Neither trait is dominant over the other, so both manifest.
What is codominant genotype?
When two alleles are codominant, that means that they are expressed simultaneously in different parts. For example, if a red and white flower were crossed, and the resulting flower had some red petals and some white petals that would be codominance. Another example is when animals have stripes and spots. Not to be confused in incomplete dominance, which is when two alleles are expressed simultaneously in the same part of the organism (in the flower example all the petals would be pink).
What is the difference between dominant and recessive gene?
There are no such things as dominant and recessive genes. There are only dominant and recessive alleles. Dominant alleles are parts of a gene that present its features over the recessive allele, which is the one that is always masked by the dominant allele. The recessive allele's trait only shows if both of the alleles in a trait are recessive.
What is expressed when both alleles for a gene are equally expressed as in human blood type?
This is called co-dominance. This is when 2 or more alleles are expressed at the same time. In other words they both affect the phenotype. In the example of human blood ABO type we have an allele for A = IA, B= Ib O=iIAIb = AB blood typeIbIb = B blood typeIai = AIaIa = A bloody typeIbi = B blood typeii = O blood type
At is a gene with two dominant alleles that are expressed at the same time?
In genetics, gene with two dominant alleles that are expressed at the same time is known as codominance. This results in a phenotype where both alleles are equally and fully expressed in the offspring. An example of codominance is the AB blood type in humans, where the A and B alleles are both expressed on the surfaces of red blood cells.
If two dominant alleles are expressed at the same time this is a case of what?
This is called codominance. In codominance, both alleles are fully expressed in the phenotype of the individual.
What term describes a gene with two dominant alleles that are expressed at the same time?
Co-dominance.
A recessive allele is represented by an letter?
In genetics, a recessive allele is typically represented by a lowercase letter. For example, if the dominant allele is represented by "A", the recessive allele for the same trait would be represented by "a".
Why are recessive alleles not always expressed as the phenotype?
Recessive alleles are not always expressed as the phenotype because an individual needs to inherit two copies of the recessive allele (one from each parent) in order for it to be expressed. If an individual inherits just one copy of the recessive allele paired with a dominant allele, the dominant allele will determine the phenotype.
Which statement is TRUE about multiple alleles?
MULTIPLE CHOICES a. It happens when two or more alleles control the inheritance of a character. b. It refers to traits that are controlled by genes located on the same-sex chromosomes. c. It occurs when two dominant alleles of a contrasting pair are fully expressed at the same time in a heterozygous individual. d. It occurs when the phenotype of the offspring is somewhere in between the phenotype of both parents.
What does co-dominant means?
Co-dominance happens when two genotypes are expressed at the same time. For example, one parent can have blood type A and one parent can have blood type B and together produce a child with blood type AB. If two parents have the blood type AB, the child has a chance of being mentally ill.
What is it called when two forms of trait are both dominant at the same time?
Codominance. It's the case of AB blood types, for instance. Neither trait is dominant over the other, so both manifest.
What is codominant genotype?
When two alleles are codominant, that means that they are expressed simultaneously in different parts. For example, if a red and white flower were crossed, and the resulting flower had some red petals and some white petals that would be codominance. Another example is when animals have stripes and spots. Not to be confused in incomplete dominance, which is when two alleles are expressed simultaneously in the same part of the organism (in the flower example all the petals would be pink).
What is it called When the heterozygotes display two phenotypes at the same time?
This is known as codominance, where both alleles in a heterozygous individual are expressed equally and simultaneously, resulting in a unique phenotype that shows characteristics of both alleles.
What is the difference between dominant and recessive gene?
There are no such things as dominant and recessive genes. There are only dominant and recessive alleles. Dominant alleles are parts of a gene that present its features over the recessive allele, which is the one that is always masked by the dominant allele. The recessive allele's trait only shows if both of the alleles in a trait are recessive.
What is a pair of nonidentical alleles affecting two phenotypes for a given trait are both expressed at same time in heterozygotes?
Codominance is when a pair of nonidentical alleles at a gene locus both affect the phenotype in heterozygotes, and therefore both alleles are expressed simultaneously. This results in the expression of a unique phenotype that is a combination of the traits associated with each allele.
