RESTRICTION ENZYMES QUESTIONS
WITH 100% CORRECT ANSWERS {
GRADED A+}
What do restriction enzymes do? - ✔✔Recognise specific sequences within a
DNA molecule (often 4-6 base pairs long) and cut them in a specific manner.
What is the natural function of a restriction enzyme? - ✔✔Their natural function
is to destroy foreign DNA entering the cell by cleaving the bacteriophage DNA to
prevent infection. The cell's own DNA is modified by methylation to protect it
from its own enzyme. Each restriction enzyme has a specific methylase.
What do type II restriction endonucleases do? - ✔✔- Recognise a specific DNA
sequence (often 4 to 6 nucleotides in length)
- Cut precisely or near this site
- Sequence often reads the same in both directions (palindromic)
, What are some examples of restriction endonucleases? - ✔✔- EcoRI from E. coli
(GAATTC, sticky)
- BamHI from Bacillus amyloliquefaciens (GGATCC, sticky)
- AluI from Arthrobacter luteus (AGCT, blunt)
- Sau3A from Staphylococcus aureus (GATC, sticky)
What are blunt ends? - ✔✔When restriction enzymes cut straight across the
double stranded DNA. Blunt ends can be re-joined regardless of the enzyme that
produced them, though with reduced efficiency compared to sticky ends as they
don't have hydrogen bonding.
What are sticky ends? - ✔✔When restriction enzymes cut in a staggered fashion
across its recognition site. They're staggered because the ends can base pair
together via hydrogen bonds, which is helpful if you want to rejoin the ends.
What is interesting about BamHI, BglIII and Sau3a? - ✔✔They recognise
different sites but produce the same sticky ends. This allows DNA fragments
produced by these different enzymes to be joined together again via base-pairing.
WITH 100% CORRECT ANSWERS {
GRADED A+}
What do restriction enzymes do? - ✔✔Recognise specific sequences within a
DNA molecule (often 4-6 base pairs long) and cut them in a specific manner.
What is the natural function of a restriction enzyme? - ✔✔Their natural function
is to destroy foreign DNA entering the cell by cleaving the bacteriophage DNA to
prevent infection. The cell's own DNA is modified by methylation to protect it
from its own enzyme. Each restriction enzyme has a specific methylase.
What do type II restriction endonucleases do? - ✔✔- Recognise a specific DNA
sequence (often 4 to 6 nucleotides in length)
- Cut precisely or near this site
- Sequence often reads the same in both directions (palindromic)
, What are some examples of restriction endonucleases? - ✔✔- EcoRI from E. coli
(GAATTC, sticky)
- BamHI from Bacillus amyloliquefaciens (GGATCC, sticky)
- AluI from Arthrobacter luteus (AGCT, blunt)
- Sau3A from Staphylococcus aureus (GATC, sticky)
What are blunt ends? - ✔✔When restriction enzymes cut straight across the
double stranded DNA. Blunt ends can be re-joined regardless of the enzyme that
produced them, though with reduced efficiency compared to sticky ends as they
don't have hydrogen bonding.
What are sticky ends? - ✔✔When restriction enzymes cut in a staggered fashion
across its recognition site. They're staggered because the ends can base pair
together via hydrogen bonds, which is helpful if you want to rejoin the ends.
What is interesting about BamHI, BglIII and Sau3a? - ✔✔They recognise
different sites but produce the same sticky ends. This allows DNA fragments
produced by these different enzymes to be joined together again via base-pairing.
