DNA: instructions inside cells — Biology, 11–13 years
DNA is a long molecule that stores information for building and running a living organism. Sections of DNA called genes help provide instructions for proteins, linking cells with inheritance and body features.
A coded set of instructions
DNA is like a long information molecule, not a tiny picture of the organism. Its chemical sequence can be read by cells; different sections, called genes, help cells make particular proteins that build structures or carry out jobs.
Why cells need DNA
A cell needs reliable information to make its parts and repeat complicated chemical jobs. DNA solves this storage problem and can be copied when cells divide. It also helps explain why offspring resemble their parents without being exact copies.
From a gene to a feature
1. A gene contains a sequence of DNA bases. 2. The cell uses that sequence as instructions for making a protein. 3. The protein may help make a pigment. 4. Pigment in the iris contributes to eye colour. This is a chain, not a single gene acting like a complete label.
One gene is not one destiny
People often say that one gene simply causes one feature, because that makes inheritance sound tidy. In reality, many features involve several genes and the environment, while one gene can affect more than one process. DNA provides instructions, not a finished life plan.
DNA in medicine and forensics
Doctors can study DNA to identify some inherited risks or choose tests that fit a person. Investigators can compare DNA patterns from a sample with known samples. These uses work because DNA varies between people, while many parts remain shared.
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