Lateral Gene Transfer The gene flow that occurs between READING TOOL individuals who may or may not be the same species is termed Connect to Visuals Figure 13-4 lateral gene flow. It is important for generating diversity among shows a normal distribution of species. Many bacteria swap their genes on plasmids. This is a polygenic trait in humans: height. What other polygenic how antibiotic resistance spreads. trait in humans might also be represented by a bell-shaped curve? Single-Gene and Polygenic Traits skin color KEY QUESTION What determines the number of phenotypes for a given trait? The number of phenotypes produced for a trait depends on how many genes control the trait. Single-Gene Traits Genes control traits in different ways. When only one gene controls one trait, this is called a single-gene trait. The trait may express itself as one or more phenotypes depending on how many alleles are present for the gene and whether alleles are dominant and recessive, incomplete, or codominant. Polygenic Traits When multiple genes control a trait, it is referred to as a polygenic trait. The influence of the environment is often important in polygenic traits. Examples of polygenic traits in humans include hair, eye, or skin color. Visual Reading Tool: Allele Frequencies 1. Calculate the allele frequency for black fur (B) and brown fur (b) in the mice population based on the number of each type of allele. Answer the questions below. Sample Population Frequency of Alleles 48% Allele for Allele for Heterozygous brown fur black fur black O 36% 16% Homozygous Homozygous Brown allele frequency: brow black Black allele frequency: 2. Which allele frequency is higher? 3. What is the genotype of a homozygous brown mouse? 4. In a population of 200 mice, how many would be homozygous black? 164 Chapter 13 Evolution of Populations Copyright @ Savvas Learning Company LLC. All Rights Reserved