Nuclease facts for kids

A nuclease is like a tiny pair of scissors inside living things. It's a special type of enzyme (a protein that helps chemical reactions). Nucleases cut the long chains of nucleic acids (like DNA and RNA). Nucleic acids are made of smaller pieces called nucleotides, and nucleases cut the links between these pieces. Two common types are deoxyribonuclease and ribonuclease.

Different Kinds of Nucleases

Nucleases come in different types, depending on where they cut. You might see the words "endo" or "exo" added to their names.

• Endonucleases are like scissors that cut a nucleic acid chain somewhere in the middle of the molecule. They don't start at the ends.
• Exonucleases are different. They work by removing nucleotides one by one from the ends of DNA molecules.

Restriction Enzymes: DNA Scissors

A special kind of nuclease is called a restriction enzyme, or more specifically, a restriction endonuclease. These enzymes have a very important and specific job.

They scan along a DNA molecule, looking for a particular sequence of nucleotides. Once a restriction enzyme finds its special sequence, it attaches to the DNA. Then, it makes a precise cut in both sides of the DNA molecule's backbone.

Different restriction enzymes cut at different specific sequences. But a single type of restriction enzyme will always cut its particular sequence in the same way, no matter what DNA it is working on. After these cuts are made, the DNA molecule breaks into smaller pieces, or fragments.

Scientists have found more than 900 different restriction enzymes from over 230 types of bacteria. These amazing tools were very important for scientists. They allowed them to "cut and paste" DNA molecules in a predictable way. Before these enzymes were discovered, cutting DNA was much harder and more random.

Images for kids

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  This image shows the crystal structure of EcoRV, which is a type of restriction enzyme, connected to a DNA molecule.