What type of graph is typically used to illustrate the phenotypic expression of polygenic traits?

A histogram is the most suitable type of graph for illustrating the phenotypic expression of polygenic traits. Polygenic traits are traits that are influenced by multiple genes, resulting in a continuous range of phenotypic expressions rather than discrete categories.

When these traits are measured in a population, the resulting data often follows a normal distribution, creating a bell-shaped curve. A histogram effectively visualizes this distribution by displaying the frequency of various phenotypic categories along the x-axis, with the height of each bar representing the number of individuals that fall within specific ranges of phenotypic expression. This makes it easier to observe how traits vary in a population and to identify patterns in the phenotypic distribution.

While other graph types like bar graphs and scatter plots have their uses, they are not ideal for depicting the frequency distribution inherent in polygenic traits. A bar graph typically represents categorical data rather than continuous data and may confuse the representation of such traits. Scatter plots are best used for displaying relationships between two quantitative variables, while a Pareto chart combines aspects of bar graphs and line graphs to highlight the most important factors in a dataset, which is not necessary for understanding polygenic inheritance specifically.