| how can wild strains of microbes be improved | mutagenesis
recombinant DNA technology |
| describe mutagenesis | exposure to UV light of other forms of radiation or mutagenic chemicals results in mutations, some of which may produce an improved strain of micro organism |
| what is recombinant DNA technology | involves the use of recombinant plasmids and artificial chromosomes as vectors |
| what is a vector | a DNA molecule used to carry foreign genetic information into another cell
both plasmids and artificial chromosomes are used as vectors during recombinant DNA technology |
| when are artificial chromosomes preferable to plasmids as vectors | when larger fragments of foreign DNA are required to be inserted |
| describe the recombinant DNA technology process | restriction endonucleases cut open plasmids and specific genes out of chromosomes leaving sticky ends.
complementary sticky ends are produced when the same restriction endonuclease (which recognises a speciifc short sequence of DNA bases) is used to cut open the plasmid and the gene from the chromosome
ligase seals the gene into the plasmid |
| what are the four parts of recombinant plasmids/artificial chromosomes | restriction sites
regulatory sequences
origin of replication
selectable markers |
| what is the function of restriction sites | contain target sequences of DNA where specific restriction endonucleases cut |
| what is the function of regulatory sequences | control gene expression |
| what is the function of the origin of replication | allows self replication of the plasmid/artificial chromosome |
| what is the function of selectable markers (eg. antibiotic resistance genes) | protect the microorganism from a selective agent (anti-biotic) that would normally kill it or prevent it from growing
Selectable marker genes present in the vector ensure that only microorganisms that have taken up the vector grow in the presence of the selective agent (antibiotic) |
| what is done to micro organisms as a safety mechanism | genes are introduced that prevent the survival of the micro organisms in an external environment |
| what is a problem with bacterial host cells | recombinant yeast cells may be used because plant or animal recombinant DNA expressed in bacteria may result in poly peptides being incorrectly folded
use of recombinant yeast cells to produce active forms of the protein which are inactive in bacteria |
