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Genes

The function of DNA is to store instructions for making proteins. This is very important because every cell needs to make a large number of different proteins in order to function.

Diagram illustrating the fact that DNA contains instructions for making proteins. On the left, there is a drawing of a group of DNA molecules, labelled "DNA". There is an arrow from this, pointing to the right, labelled "...contains instructions for making...". This arrow points to a drawing of a group of proteins (illustrated as colourful blobs), labelled "Proteins".

DNA contains instructions for making proteins.

A gene is a section of a DNA molecule that codes for a protein

A single DNA molecule usually contains instructions for making multiple proteins. Different sections of the DNA molecule contain the instructions for making different proteins. These sections of the DNA molecule are called genes.

A gene is a section of a DNA molecule that contains the instructions for making a particular protein. Another way of saying this is to say that the gene 'codes for' the protein.

Diagram illustrating the nature of a gene. A DNA molecule (in the form of a double-helix) is shown running horizontally across the diagram. One section of the DNA molecule has a box around it. This is labelled, "Gene. A section of a DNA molecule that codes for a protein". An arrow from the gene points to a drawing of a protein, labelled "Protein". A label on the arrow explains, "The cell follows the instructions in the gene to make the protein".

A gene is a section of a DNA molecule that codes for a protein. In other words, the gene contains the instructions that the cell follows in order to make the protein.

Within the DNA of an organism there are genes for every protein that the organism produces.

The base sequence of a gene determines the amino acid sequence of the protein that it codes for

Every protein has a unique shape which allows it to carry out its function. For example, an enzyme has an active site which is shaped to fit its substrates, and a protein which is a receptor for a hormone has a shape which allows it to bind to that hormone.

The unique shape of each protein is a result of the unique sequence of amino acids that make it up. A protein is made by joining together amino acids into a chain which then folds up to form the final shape of the protein. If the amino acid sequence was different, the protein would fold up into a different shape.

When a cell makes a protein, the gene acts as a set of instructions telling the cell how to make the protein. Each gene has a unique sequence for bases which determines the amino acid sequence of the protein that it codes for.

Diagram illustrating the relationship between a gene and the protein that it codes for. On the left there is a diagram of a DNA double-helix. The bases are labelled with their letters (ACGCTAG and so on). Above this is written, "The sequence of bases in the gene". Then there is an arrow to the right, which is labelled "...determines...". Then there is a drawing of a chain of amino acids labelled, "The sequence of amino acids". Then there is another arrow to the right labelled "...determines...". Then there is a drawing of the same chain of amino acids but now folded up into a protein. It is labelled "The shape of the protein". So overall, the text reads: "The sequence of bases in the gene determines the sequence of amino acids [which] determines the shape of the protein".

The sequence of bases within a gene determines the sequence of amino acids in the protein that it codes for. This then determines the shape of the protein, which is essential to the protein's function.

Flashcards

Flashcards help you memorise information quickly. Copy each question onto its own flashcard and then write the answer on the other side. Testing yourself on these regularly will enable you to learn much more quickly than just reading and making notes.

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What is the function of DNA?

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What is a gene?

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How does a gene code for a protein?

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