How do multiple alleles differ from simple Mendelian inheritance?

How do multiple alleles differ from simple Mendelian inheritance?

• A. Multiple alleles affect only one trait
• B. Multiple alleles involve more than two alleles for a gene
• C. Simple Mendelian traits have no dominant alleles
• D. Multiple alleles are always recessive

Answer: (B)

The correct choice highlights that multiple alleles involve more than two different forms of a gene for a particular trait, which extends the concept of Mendelian inheritance. In simple Mendelian inheritance, a gene typically has only two alleles, one from each parent, which can be dominant or recessive. For example, in a classic Mendelian trait, like flower color in peas, you may have one allele for purple flowers and another for white flowers. However, in cases of multiple alleles, such as the ABO blood type system, there are three different alleles: A, B, and O. Individuals can inherit any two of these alleles, leading to four possible blood types: A (only A alleles), B (only B alleles), AB (one A and one B allele), and O (two O alleles). This complexity allows for a greater variety of phenotypes and genetic outcomes compared to simple Mendelian traits where variation is limited to two alleles. Understanding this distinction helps illustrate the broader and more complex rules of inheritance that can occur beyond simple dominant-recessive relationships defined by Mendel's original work.

The correct choice highlights that multiple alleles involve more than two different forms of a gene for a particular trait, which extends the concept of Mendelian inheritance. In simple Mendelian inheritance, a gene typically has only two alleles, one from each parent, which can be dominant or recessive. For example, in a classic Mendelian trait, like flower color in peas, you may have one allele for purple flowers and another for white flowers.

However, in cases of multiple alleles, such as the ABO blood type system, there are three different alleles: A, B, and O. Individuals can inherit any two of these alleles, leading to four possible blood types: A (only A alleles), B (only B alleles), AB (one A and one B allele), and O (two O alleles). This complexity allows for a greater variety of phenotypes and genetic outcomes compared to simple Mendelian traits where variation is limited to two alleles.

Understanding this distinction helps illustrate the broader and more complex rules of inheritance that can occur beyond simple dominant-recessive relationships defined by Mendel's original work.