The Discovery
Who were the three scientists credited with discovering restriction enzymes in the 1960s?
Werner Arber, Hamilton O. Smith, and Daniel Nathans.
What does the restriction enzyme EcoRI recognize and cut?
The sequence GAATTC.
Name one medical application of restriction enzymes.
Producing insulin by inserting the human insulin gene into bacterial plasmids.
What must be done to a plasmid before a gene of interest can be inserted?
The plasmid must be cut open with a restriction enzyme.
What is the purpose of introducing recombinant plasmids into bacteria?
To make the bacteria produce proteins, like insulin, encoded by the inserted gene.
What biological system were scientists studying when they discovered restriction enzymes?
Bacterial defense systems against viruses.
What type of ends do some restriction enzymes, like EcoRI, leave after cutting DNA?
Sticky ends.
How are restriction enzymes used in forensics?
The conviction of Colin Pitchfork in 1987.
Why must the same restriction enzyme be used on both the plasmid and the gene of interest?
To ensure the sticky ends are complementary and can join properly.
What is the process called that makes bacteria take up plasmids?
Transformation
What award did the discovery of restriction enzymes earn, and in what year?
The Nobel Prize in Medicine, 1978.
Why are sticky ends important in genetic engineering?
They allow complementary DNA fragments to pair and join, enabling recombination.
What was the name of the first criminal case solved using DNA evidence and restriction enzymes?
The conviction of Colin Pitchfork in 1987.
What role does DNA ligase play in creating recombinant DNA?
It seals the sticky ends of the DNA fragments by forming covalent bonds.
Why are antibiotic resistance genes included in recombinant plasmids?
To identify bacteria that have successfully taken up the plasmid by growing them on antibiotic plates.
What is the specific term for the DNA sequences that restriction enzymes recognize and cut
Palindromic sequences.
How does a restriction enzyme ensure it only cuts at specific sites on DNA?
It recognizes a specific palindromic sequence and binds only to that sequence.
Why is gel electrophoresis necessary after DNA is cut by restriction enzymes in forensics?
To separate DNA fragments by size and visualize unique patterns for DNA fingerprinting.
Describe the process of inserting a human gene, such as the insulin gene, into a plasmid.
The plasmid and human DNA are cut with the same restriction enzyme, the insulin gene is inserted into the plasmid using matching sticky ends, and DNA ligase seals the fragments.
What is one reason bacteria might fail to grow on antibiotic plates after transformation?
The bacteria did not take up the plasmid, or the plasmid was not properly sealed with DNA ligase.
Why are restriction enzymes described as "molecular scissors," and how do they benefit bacteria?
They cut viral DNA at specific sequences, preventing viruses from infecting bacterial cells.
Explain the difference between sticky ends and blunt ends, and give an example of a restriction enzyme for each.
Sticky ends have overhangs (e.g., EcoRI), while blunt ends are straight cuts (e.g., SmaI).
How do restriction enzymes contribute to paternity testing?
They cut DNA into fragments that can be compared between parent and child to establish familial relationships.
What could happen if the restriction enzyme used to cut the DNA doesn’t function properly during the recombinant DNA process?
The plasmid may not open, preventing the insertion of the gene of interest, and the process would fail.
Explain how heat shock is used in bacterial transformation and why it is effective.
Heat shock temporarily makes the bacterial cell membrane more permeable, allowing the plasmid to enter the cell.