Explain what codominance and incomplete dominance are (include the re.pdf

Explain what codominance and incomplete dominance are (include the relationship between the
alleles).
Solution
Alleles are the two or more alternative forms of a gene that are found at the same locus in either
of the chromosomes of a pair.
Dominance describes the relationship between alleles of a specific gene in terms of phenotypic
expression of the character that each allele of this gene represents. The dominant allele of a gene
controls the associated phenotypic character in the heterozygous condition that is when the other
form of the allele which is recessive, is also present.
A recessive allele needs to be homozygous (that is both the allelic forms of a particular gene that
are present are recessive only) then only the phenotypic character that it represents could be
observed/visible.
In the case of codominance, both the forms of alleles for a gene are dominant. That is, the
phenotypic effect represented by both of them is observed/visible. For example, the color of
cattle which may be red or white. But when both the alleles for the color of the cattle (for red and
white colors) are dominant, in progeny, you get cattle with both the colors (roan) which is
because both the alleles for color are expressed equally, as a result, both the parental traits appear
altogether. This is co-dominance. The effect of both the genes cannot be quantified.
In the case of incomplete dominance, the dominant allele is unable to express itself completely
and we get the phenotypic effect that is a mix (blending) of the effect of the dominant allele as
well as of recessive allele of a gene. As a result, a cross between two organisms with different
phenotypes represented by the alternative forms of alleles of a gene, we get offsprings/progeny
with a new phenotype that is a result of mixing of both the parental phenotypes. For example, a
cross between plants with red flowers and white flowers will result in pink flowers in the
progeny (which will be heterozygotes), if there is co-dominance. Incomplete dominance can be
quantified..

1. Explain what codominance and incomplete dominance are (include the relationship between the
alleles).

Solution

Alleles are the two or more alternative forms of a gene that are found at the same locus in either
of the chromosomes of a pair.
Dominance describes the relationship between alleles of a specific gene in terms of phenotypic
expression of the character that each allele of this gene represents. The dominant allele of a gene
controls the associated phenotypic character in the heterozygous condition that is when the other
form of the allele which is recessive, is also present.
A recessive allele needs to be homozygous (that is both the allelic forms of a particular gene that
are present are recessive only) then only the phenotypic character that it represents could be
observed/visible.
In the case of codominance, both the forms of alleles for a gene are dominant. That is, the
phenotypic effect represented by both of them is observed/visible. For example, the color of
cattle which may be red or white. But when both the alleles for the color of the cattle (for red and
white colors) are dominant, in progeny, you get cattle with both the colors (roan) which is
because both the alleles for color are expressed equally, as a result, both the parental traits appear
altogether. This is co-dominance. The effect of both the genes cannot be quantified.
In the case of incomplete dominance, the dominant allele is unable to express itself completely
and we get the phenotypic effect that is a mix (blending) of the effect of the dominant allele as
well as of recessive allele of a gene. As a result, a cross between two organisms with different
phenotypes represented by the alternative forms of alleles of a gene, we get offsprings/progeny
with a new phenotype that is a result of mixing of both the parental phenotypes. For example, a
cross between plants with red flowers and white flowers will result in pink flowers in the
progeny (which will be heterozygotes), if there is co-dominance. Incomplete dominance can be
quantified.