2.7 Genetic Control of Metabolism Flashcards
(23 cards)
State the two main ways that a microorganisms DNA can be changed?
- Mutagenesis
- Recombinant DNA technology
Define ‘wild type’
the typical form of a species that is found in nature
Define ‘mutagenesis’
the creation of mutations using radiation or mutagenic chemicals
How is mutagenesis done?
Exposing organisms to UV light (or other radiation) or mutagenic chemicals
Define ‘recombinant DNA technology’
another name for genetic engineering
Describe a vector in the context of recombinant DNA technology
a DNA molecule used to carry foreign genetic information into another cell
Give two examples of vectors used in recombinant DNA technology
- Plasmid
- Artifical chromosome
Explain why an artifical chromosome would be used instead of plasmid
Artificial chromosomes are preferable to plasmids as vectors when larger fragments of foreign DNA are required to be inserted.
Define ‘restriction endonuclease’
an enzyme which cuts a DNA sequence at specific sites producing ‘sticky ends’
Give the function of a restriction endonuclease
- Remove genes from chromsomes
- Cut open plasmids
Explain how a restriction endonuclease works
- Each restriction endonuclease recognises a specific target sequence of DNA called a restriction site.
- The same restriction endonuclease is used to cut open the plasmid AND remove the gene from the chromosome.
- Using the same restriction endonuclease for both produces complementary sticky ends allowing the gene to be inserted into the plasmid.
Explain what a ‘sticky end’ means
A piece of DNA that has been cut to produce complementary bases to another section of cut DNA allowing them to be joined together
State the enzyme that joins ‘stick-ends’ together
Ligase will seal the gene into the plasmid
Describe the steps for how a restriction endonuclease and ligase work
- Restriction sites contain target sequences of DNA where specific restriction endonucleases cut.
- Restriction endonucleases cuts open plasmids and specific genes out of chromosomes, leaving complementary sticky ends.
- Complementary sticky ends are produced when the same restriction endonuclease is used to cut open the plasmid and the gene from the chromosome.
- Ligase seals the gene into the plasmid.
Define ‘ligase’
DNA ligase is an enzyme which seals cut DNA together
Define ‘regulatory sequence’
Sequences on vectors that control gene expression
Define ‘origin of replication’
Sequences on vectors that allow self-replication of the plasmid/artificial chromosome
Define ‘selectable marker’
genes present in the vector ensure that only micro-organisms that have taken up the vector grow in the presence of the selective agent.
Give an example of a common selectable marker using in recombinant DNA technology
Antibiotic resistance gene
Explain how a selectable marker works
The genes used are often antibiotic resistance genes, so only the micro-organisms that have been genetically modified (and so has the antibiotic resistance gene) will survive the selective agent (antibiotic) and grow.
Explain how scientists ensure genetically modified microorganisms don’t survive outside the lab
external environment genes are often introduced that prevent the survival of the microorganism outside a lab.
Why would a recombinant yeast cell be used instead of a bacteria?
Plant or animal recombinant DNA expressed in bacteria may result in polypeptides being incorrectly folded, meaning it is non-functional. Yeast are eukaryotes so don’t have the same issue.
What does recombiant mean?
An organism that has been genetically modified
