Scientists might have solved the mystery of why all animals need sleep to survive
Scientists know that we need sleep to survive but until now they didn’t know why. New research suggests it’s all to do with keeping up essential repairs
READING LEVEL: GREEN
Scientists know we need sleep to survive. We know it too, unless perhaps we’re overtired and not thinking straight.
But until now, not even scientists knew why we need sleep.
A new study just published in the science journal Nature Communications shows we need sleep because that’s when our body repairs the DNA in our nerves*.
DNA is a tiny structure in every cell* in our body that carries the instructions about how our body should grow and function.
When we’re awake, broken DNA builds up in our nerve cells in our brains. It’s not until we are asleep the repairs can happen quickly enough to keep up with breakages.
It’s a bit like taking a car to a mechanic to repair a problem that gets worse every time you drive it. A mechanic can’t repair the car while it’s going at 100kmh on a freeway.
Animals as simple as worms and as complex as humans all sleep.
Scientist Lior Applebaum from Bar-Ilan University in Israel thought that if sleep was so common, it must be to do with something all animals have, which is a nervous system*.
Professor Applebaum and his student David Zada bred zebrafish* so there were tiny chemical markers, like a microscopic tag or flag, that the scientists could see on the DNA in nerve cells of the fish. Using a powerful microscope, they watched what happened to the DNA while the fish were awake and asleep.
They saw that when the fish were awake, the repair couldn’t keep up with the damage that happened to DNA as part of normal life. If the scientists kept the fish awake by tapping on the fishtank, the damage was so great the fish were in danger of dying.
When the fish were asleep, the rate of the damage reduced and the rate of repair sped up.
“It’s surprising, because the brain goes into a rest state, but the chromosomes move about twice as much during sleep,” Prof Appelbaum told the Guardian. Chromosome is the name for a threadlike arrangement of DNA in our cells, like a string of beads.
“There is repair going on in the day, but sleep allows you to catch up.”
This is the second recent study that suggests we need to sleep to repair DNA.
Siu-Wai Choi at Hong Kong University tested blood samples from doctors who had to stay awake at work for many hours. She found more DNA damage in the samples than if the doctors had been able to sleep.
GLOSSARY
- nerves: specialised cells in our body that carry messages as tiny electrical signals
- cell: basic unit of living things
- nervous system: network of nerve cells and fibres around the body
- zebrafish: small freshwater fish native to the Himalayas common as pets in fishtanks
EXTRA READING
Apple’s iSheet invention for a better night’s sleep
Car that drives itself while you catch up on sleep
QUICK QUIZ
- What is DNA and where is it?
- What sort of fish did they use? What do you now know about these fish?
- What happened if the scientists kept the fish awake?
- What are chromosomes?
- Describe another recent study about sleep and DNA.
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CLASSROOM ACTIVITIES
1. Sleep
Design two posters or information sheets that will help parents or carers understand why kids need a good night’s sleep. Use the information in the story for one poster or sheet, then create another one based on your own ideas. Make them interesting and eye-catching!
Time: allow 30 minutes to complete this activity
Curriculum Links: English, Media Arts, Critical and Creative Thinking
2. Extension
Write a bedtime story for someone your age. Your story should help the person reading it to relax and to think of good things before they go to sleep - and hopefully have good dreams. Include pictures or illustrations.
Time: allow 25 minutes to complete this activity
Curriculum Links: English, Visual Arts
VCOP ACTIVITY
After reading the article, with a partner, highlight all the openers you can find in blue. Discuss if they are powerful and varied openers or not. Why do you think the journalists has used a mix of simple and power openers? Would you change any, and why?
HAVE YOUR SAY: Describe what happens to your body and behaviour when you’re tired. Do you think the scientists are right?
No one-word answers. Use full sentences to explain your thinking. Your answers will not show until approved by editors.