How DNA changes over time is a huge and fascinating subject and you may want to learn more. Here are some questions and links to get started.

Are there different kinds of mutations?

Yes. Scientists categorize mutations by where they happened, how much DNA is affected, and the type of change that happened.

What is a Mutation? (Genetic Science Learning Center)

DNA is Constantly Changing through the Process of Mutation (Scitable, Nature Education)

Are mutations good or bad?

Well, it depends. This web site focuses on how we have benefited from mutations to our food crops. The thing to remember is that humans select plants for traits that we like. Plant mutations that we don't want are rejected, even if they would help the plant survive on its own. For instance, we may choose a lemon tree without thorns over a tree that is very thorny.

Even in people, some mutations may help them to survive in one situation, but be harmful in others. One interesting example is sickle cell anemia. If you get one copy of the mutated gene it can help you to survive malaria. If you get two copies of the mutated gene it can make you ill.

A Mutation Story (video-PBS)

Is DNA the only structure that holds genetic information?

No. RNA can also carry genetic information.

Messenger RNA carries the genetic code from the nucleus to the mitochondria. RNA is similar to DNA except that it usually is shorter and often single stranded. As the initials indicate, its structure has a ribose instead of a deoxyribose. Different types of RNA are active in many cell functions.

Viruses have either RNA or DNA for their genetic material.

Can our genetics change in other ways?

Yes. One area that scientists are really excited about is epigenetics. Genes get turned on or off depending on what an organism needs. This helps the organism respond to changes in the environment. The interesting part is that this control over the gene can be passed from one generation to another. Even though the DNA sequence of bases hasn't changed, the traits you see change. Here are some sites to learn more:

Epigenetics (Genetic Science Learning Center)

Epigenetics (video-NOVA)