DNA damage theory of ageing facts for kids

The DNA damage theory of ageing suggests that our bodies get older because our DNA gets damaged over time. Even though our cells have amazing ways to fix most of this damage, some of it still builds up. This build-up of damage can make our cells and bodies not work as well as they used to.

Most of the time, when we talk about DNA damage and ageing, we are focusing on the DNA found in the main part of the cell, called the cell nucleus. However, tiny powerhouses in our cells, called mitochondria, also have their own DNA that can get damaged.

What is DNA?

DNA stands for deoxyribonucleic acid. It's like a special instruction book found inside almost every cell in your body. This book contains all the information your body needs to grow, develop, and work properly. It tells your cells what to do and how to make everything from your hair color to how your heart beats.

Where is DNA Found?

Most of your DNA is stored safely inside the cell nucleus of each cell. Think of the nucleus as the cell's control center. But there's also a smaller amount of DNA in the mitochondria. These are like the cell's power plants, making energy.

How Does DNA Get Damaged?

DNA is very important, but it can get damaged in many ways. Imagine a book getting torn pages or smudged words. DNA can get similar "tears" or "smudges."

Everyday Damage

• From inside your body: Your body is always doing chemical reactions to stay alive. Sometimes, these reactions create harmful molecules called "free radicals." These can bump into DNA and cause damage.
• From outside your body: Things like sunlight (UV rays) or certain chemicals in the environment can also harm your DNA.

Types of DNA Damage

DNA damage can be small changes to its chemical structure. It can also be breaks in the DNA strands. Even a single cell can experience thousands of DNA damage events every day!

How Do Cells Try to Fix DNA?

Luckily, your cells are super smart and have many ways to fix DNA damage. Think of them as tiny repair crews working non-stop.

DNA Repair Mechanisms

• Proofreading: When DNA is copied, special enzymes check for mistakes and fix them right away.
• Excision repair: If a small part of the DNA is damaged, the cell can cut out the bad piece and replace it with a new, correct one.
• Double-strand break repair: If both strands of the DNA are broken, the cell has emergency systems to try and stick them back together.

These repair systems are very efficient. They fix most of the damage that happens.

Why Does Damage Build Up?

Even with all these amazing repair systems, some DNA damage still builds up over time. This happens for a few reasons:

• Too much damage: Sometimes, there's just too much damage happening for the repair crews to keep up.
• Less efficient repair: As we get older, our repair systems might not work as well as they used to. They might become slower or make more mistakes.
• Mistakes in repair: Sometimes, when the cell tries to fix DNA, it might make a new mistake, or it might not fix it perfectly.

When DNA damage builds up, it can cause problems. Cells might not be able to read their instructions correctly. This can lead to cells not working properly, or even dying. Over many years, this build-up of damage across many cells is thought to be a big reason why our bodies age.