• Genetic Variation
• Mutations
  • Mutations are random
  • The Lederberg experiment
• Causes of mutations
  • Reviewing DNA
  • Types of mutations
  • Case study: sickle cell anemia
• Gene flow
  • Gene flow: details
• Sex and genetic shuffling
  • Sex and genetic shuffling: details
• Development
  • Types of developmental change
  • Ontogeny and phylogeny
  • Developmental constraints
  • Understanding complexity
  • Hox genes

The Causes of Mutations

Mutations happen for several reasons.

1. DNA fails to copy accurately.
   Most of the mutations that we think matter to evolution are “naturally-occurring.” For example, when a cell divides, it makes a copy of its DNA—and sometimes the copy is not quite perfect. That small difference from the original DNA sequence is a mutation.
   
2. External influences can create mutations.
   Mutations can also be caused by exposure to specific chemicals or radiation. These agents cause the DNA to break down. This is not necessarily unnatural—even in the most isolated and pristine environments, DNA breaks down. Nevertheless, when the cell repairs the DNA, it might not do a perfect job of the repair. So the cell would end up with DNA slightly different than the original DNA and hence, a mutation.

	•	Reviewing DNA
	•	Types of mutations
	•	Case study: sickle cell anemia

	Lesson plans for teaching about mutation