Humber Admissions Practice Test

What characterizes polygenic inheritance?

1. Only one set of alleles governs a trait

2. Two or more sets of alleles influence a single trait

3. Traits that follow a simple Mendelian pattern

4. Only environmental factors influence trait expression

The correct answer is: Two or more sets of alleles influence a single trait

Polygenic inheritance is characterized by two or more sets of alleles influencing a single trait. This means that multiple genes contribute to the expression of a single phenotypic trait, resulting in a range of possible outcomes. For example, traits like height, skin color, and eye color in humans are often determined by several different genes, each with their contributions to the overall characteristic. This is in contrast to traits that are controlled by a single gene, where the inheritance pattern is typically straightforward, following Mendelian principles. The other choices do not accurately describe polygenic inheritance. When only one set of alleles governs a trait, it suggests a monogenic trait, which is not representative of polygenic inheritance. Traits that follow a simple Mendelian pattern also do not exhibit polygenic characteristics, as those traits arise from single allele interactions. Lastly, while environmental factors can influence trait expression, they do not negate the role of genetics in polygenic inheritance, which is defined by the additive effects of multiple genes rather than the absence of genetic influence.