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Science

How genes control growth and development

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Genes are sections of DNA. Each gene is a set of coded instructions for making a particular protein.

The genetic code

DNA is a chemical code, or set of instructions. Our bodies need proteins for growth and development, and the DNA controls which proteins are made. The code consists of four different chemicals, or bases, that always pair up in the same way.

DNA shown as a double twisted string with interlinking parts

Base pairs on a DNA molecule

T always pairs with A

G always pairs with C

The order of these pairs of bases along the DNA molecule codes for all the different proteins. A section of DNA that codes for one particular protein is called a gene. Each chromosome contains thousands of different genes.

The genetic code of the DNA always remains safe inside the nucleus [nucleus: The central part of an atom. It contains protons and neutrons, and has most of the mass of the atom. ]. But the proteins are made outside the nucleus in the cytoplasm of the cell. For this to happen, a copy of the genetic code of a gene is made. This copy then passes out of the nucleus into the cytoplasm where the protein is made.

chromosome, showing gene as section of DNA

Nucleus, chromosome and gene

Read on if you are taking the Higher paper.

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