Which of the following is an example of a gene that has multiple alleles?

Which of the following is an example of a gene that has multiple alleles?

• A. The gene for flower color in roses
• B. The ABO blood group system
• C. The gene for eye color
• D. The gene for coat color in cats

Answer: (B)

The ABO blood group system is an excellent example of a gene that has multiple alleles. In this system, the gene responsible for blood type has three main alleles: A, B, and O. Each individual inherits two of these alleles, one from each parent, resulting in four possible blood types: A, B, AB, and O. This characteristic illustrates the concept of multiple allelism, where more than two alleles exist within a population, providing a richer genetic diversity than is present with simple Mendelian traits. In contrast, the other options describe genes that may exhibit variation but do not fit the criteria of being controlled by multiple alleles in the same way. For instance, while the gene for flower color in roses may have several variations, it does not exemplify the complexity seen in a system like ABO, where the presence of different combinations of alleles leads to distinct phenotypic expressions. Similarly, the genes for eye color and coat color in cats are typically influenced by fewer alleles, often demonstrating simple inheritance rather than the multiple allele scenario as seen with the ABO blood group.

The ABO blood group system is an excellent example of a gene that has multiple alleles. In this system, the gene responsible for blood type has three main alleles: A, B, and O. Each individual inherits two of these alleles, one from each parent, resulting in four possible blood types: A, B, AB, and O. This characteristic illustrates the concept of multiple allelism, where more than two alleles exist within a population, providing a richer genetic diversity than is present with simple Mendelian traits.

In contrast, the other options describe genes that may exhibit variation but do not fit the criteria of being controlled by multiple alleles in the same way. For instance, while the gene for flower color in roses may have several variations, it does not exemplify the complexity seen in a system like ABO, where the presence of different combinations of alleles leads to distinct phenotypic expressions. Similarly, the genes for eye color and coat color in cats are typically influenced by fewer alleles, often demonstrating simple inheritance rather than the multiple allele scenario as seen with the ABO blood group.