Question

A relationship among alleles where both alleles contribute to the phenotype of the heterozygote is

Answer 1

A relationship among alleles where both alleles contribute to the phenotype of the heterozygote is codominance, where both alleles are fully and simultaneously expressed. In contrast, incomplete dominance results in an intermediate phenotype. An example of codominance is the ABO blood group system, and an example of incomplete dominance is the pink flowers of heterozygote snapdragons.

Step-by-step explanation:

A relationship among alleles where both alleles contribute to the phenotype of the heterozygote is known as codominance. This is a genetic scenario where both alleles for the same characteristic are simultaneously and completely expressed in the heterozygote. In contrast, incomplete dominance is a pattern of inheritance where the heterozygote expresses an intermediate phenotype between the dominant and recessive phenotypes, neither allele being completely dominant over the other.

An example of codominance is seen in the ABO blood group system, where both A and B alleles are expressed in individuals with the AB blood type. This is in contrast to the incomplete dominance example of flower color in snapdragons, where a cross between a red-flowered plant and a white-flowered plant results in offspring with pink flowers – an intermediate phenotype.

Geneticists can predict the outcome of crosses involving codedominance or incomplete dominance. With codominance, a self-cross between heterozygotes expressing a codominant trait would yield offspring with a 1:2:1 genotypic ratio, while phenotypically exhibiting three distinct types. Similarly, in incomplete dominance, crossing two intermediate phenotypes (monohybrid heterozygotes) can also result in a 1:2:1 phenotypic ratio.

Answer 2

A relationship among alleles where both alleles contribute to the phenotype of the heterozygote is codominance.

This is a phenomenon when both alleles are fully expressed. As a result, offspring will have a phenotype that is neither dominant nor recessive, it is combination of both. For example, if one allele contributes to white color of flower, another allele contributes to red color, the offspring (if we cross those two flowers) will have pink flowers (both phenotypes expressed).