DNA is a long, chain-like molecule made up from nucleotides. Each nucleotide can be one of four different kinds – an A, C, G, or T. The identity and order of these nucleotides is very important and is called the DNA sequence. Like the letters in a word, DNA sequences convey information. In the case of DNA, this information is used as a recipe for making proteins. In turn, the proteins are the building blocks that make up the cells in our bodies.

A mutation is a permanent change or variation in the DNA sequence. This change can be simple, like a difference in the letters of a gene (such as an A changing to a C). Or, it can be more complex, like the deletion of a whole region within the DNA. Some mutations are common and occur frequently in humans, resulting in things like different hair or eye color.

Mutations can happen at any time and in any cell during an organism’s lifetime. Some mutations occur because of errors in copying the DNA during cell duplication. Others are caused by environmental factors like UV radiation or exposure to chemicals. Mutations in germ cells (eggs or sperm) can be passed onto the next generation. Here’s an example of a mutation in zebrafish, along with the DNA sequence of the mutated gene:

1) What is the difference between the two DNA sequences?

2) What is the result of that difference?

3) Do you think this result is harmful to the zebrafish?

4) How do you think mutations can be used in science research?