1.1 From genetic information to protein function

Almost every process in a cell requires proteins. As you saw in Week 2, antibiotics often exert their bactericidal and bacteriostatic effects by binding to proteins that are crucial to the structure or function of the bacterial cell.

The function of a protein is largely determined by its structure. Proteins are comprised of building blocks called amino acids. The sequence of these amino acids determines the structure of a protein. The amino acid sequence of a protein is specified by the DNA sequence of a gene (Figure 1). So, there is a direct relationship between DNA and the structure and function of a protein.

Figure 1 The DNA sequence of a gene encodes the sequence of amino acids in a protein.

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This figure is a schematic diagram showing three genes 1, 2 and 3, at different locations within the genome. Each gene is expressed (via transcription and translation) as a chain of amino acids in a specific sequence – chains 1, 2 and 3 respectively. Each amino acid chain then folds up into a particular three-dimensional structure, determined by its amino acid sequence.

Figure 1 The DNA sequence of a gene encodes the sequence of amino acids in a protein.

In 1958, Francis Crick, who helped discover the structure of DNA, proposed the central dogma to explain how genetic information, encoded in DNA, can be converted into a functional product, a protein. The following short video gives an overview of this central dogma. Note that the conversion of information, encoded in DNA, into a protein occurs via an intermediate molecule called RNA (ribonucleic acid).

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Transcript: Video 2 An overview of the flow of information from DNA to protein.

NARRATOR:

To make a particular protein in the cell, the relevant gene is first switched on in the DNA. A working copy of the gene, called messenger RNA, is made. This copying process is called transcription. Next, the information in the messenger RNA is acted upon to produce a protein.

End transcript: Video 2 An overview of the flow of information from DNA to protein.

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Video 2 An overview of the flow of information from DNA to protein.