20.1 Genes contain genetic information
20.2 Alleles are dominant or recessive
20.3 The inheritance of alleles can be described in a diagram
20.4 Properties of a single gene
20.5 How can parents with freckles have a child without freckles?
20.6 Genes affect many of our traits
20.7 Acquired traits
20.8 The function of genes is complex
20.9 Sex-linked inheritance
20.10 Mutations are errors in genetic information
20.11 Genes and diseases