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7. Beskrive brugen af rekombinant DNA-teknologi til kloning af eukaryote gener

Few terms are necessary to be understood:

Gene cloning – a DNA sequence, such as a gene, that is transferred from one organism to another and expressed in the new organism.

Recombinant DNA - combination of two DNA fragments of different origin into one DNA molecule by the use of restriction enzymes and DNA ligase.

Vector – an agent, such as a virus or a plasmid, which carries a modified foreign gene.

Both the eukaryotic gene and the plasmid have to be introduced to the same restriction endonuclease. This enzyme cleaves them both in specific sequences, leaving sticky ends that will later bind to each other forming a recombinant DNA molecule.  

Plasmids are the most often used cloning vectors for expressing eukaryotic genes since they are independent from the rest of the cell and their expression solely depends on enzymes that have a long half-life.  

When the plasmid is introduced into the host cell, they express the eukaryotic gene that is incorporated in their genome. The use of transgenic animals has shown that the exons are spliced correctly.

If the eukaryotic gene should be express in a prokaryotic cell, cDNA should be used and the protein should be shielded from the degrading enzymes of the prokaryotic cell. The principle of cloning is the same.

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