higher biology - unit 2.7: genetic control of metabolism

wild strain

the typical form, existing in nature, non-mutated version

a wild strain that produces a desired trait may still lack other important features such as...

genetic stability, ability to grow on low cost nutrients, overproduction of desired products, easy harvesting of product

how can wild strains be improved?

mutagenesis and recombinant DNA technology

exposure to UV light and other forms of radiation or mutagenic chemicals result in...

mutations, some of which may produce an improved strain

recombinant DNA technology

involves the use of recombinant plasmids and artificial chromosomes as vectors

vector

dna molecule use to carry foreign genetic information into another cell

what can a microbe be genetically modified to produce?

substances useful to human e.g. human insulin

where are artificial chromosomes preferable to plasmids?

as vectors when larger fragments of foreign DNA are required to be inserted

what cuts open plasmids?

restriction endonucleases

genetic engineering step 1

select a particular DNA sequence for a desirable characteristic from the donor organism

genetic engineering step 2

splice it into the DNA of a vector

genetic engineering step 3

insert the vector into the host cell

what leaves sticky ends?

restriction endonucleases when they cut open plasmids and specific genes

how are complementary sticky ends produced?

when the same restriction endonuclease is used to cut open the plasmid and the gene from the chromosome

what seals the gene into the plasmid?

ligase

restriction sites

contain target sequences of DNA where specific restriction endonucleases cut

regulatory sequences

control gene expression

origin of replication

allows self-replication of the plasmid or artificial chromosome

why is the origin of replication important?

allows many copies to be made, meaning the product can be produced by fewer cells

selectable markers

such as antibiotic resistance, protect micro-organisms from a selective agent that would normally kill them or prevent their growth

what is the purpose of antibiotic resistance genes in selectable markers?

ensure that only micro-organisms that have taken up the vector grow in the presence of the selective agent

as a safety mechanism, genes are often introduced that prevent...

the survival of the micro-organism in an external environment

what can be genetically modified to produce active forms of the protein which are inactive in bacteria?

yeast cells

what can result in polypeptides being folded incorrectly?

plant or animal recombinant DNA expressed in bacteria

recombinant plasmids and artificial chromosomes contain...

restriction sites, regulatory sequences, and origin of replication and selectable markers