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