From Seed to Seed:
Plant Science for K-8 Educators

Mutations

Random genetic mutations in a plant or animal can result in characteristics that are beneficial-or those that are harmful-to the plant. What exactly is a mutation, and how does one occur?

A mutation is a random change in the DNA sequence that is passed down to offspring. For the most part, the replication of chromosomes preceding cell division is flawless, and results in an identical copy. However, occasionally random errors in the coding occur. These errors, or variations, are called mutations.

What types of mutations are beneficial to an organism? One example would be a mutation that gave a plant a bitter taste; this would discourage herbivores from eating it. This plant would therefore have an advantage over its tasty relatives, and would survive to reproduce, passing on the bitterness to its offspring.

Other mutations cause harm to the organism. These mutations might affect, for example, a plant's resistance to disease, ability to photosynthesize, or other factors influencing its ability to compete. Most harmful mutations don't persist for long in a species, because the affected individuals don't survive to reproduce.

And finally, many mutations are believed to have no effect whatsoever on the organism.

It is mutations-or changes in the DNA sequence-that provide the original source of all variation. A great way to introduce the concept of mutations to your students is through baking! Suppose you were to hand out identical copies of a cookie recipe-say, chocolate chip-to each of your students. Each student is asked to take the recipe home, bake a batch, and bring some back to the classroom. Barring any environmental influences (which can be useful in explaining the effect of environmental factors on gene expression), these batches of cookies should be very similar. If you were instead to hand out recipes that were slightly different, the cookies-due to these "mutations"-would look and taste very different. Variations may include using half the amount of sugar, flour, or chocolate chips in the original recipe, not using vanilla, or using cold vs. room-temperature eggs. Bring in some milk and have students do a taste test to determine whether the mutations were beneficial, harmful, or neutral!