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Restriction Digest Activity: Exit Ticket
Name ________________ Per____
Today, you performed a restriction digest of 6 different DNA samples. You did this as a
step towards finding out “who done it.”
1) What were the names of the 6 DNA samples?
2) How many suspects are there in this activity?
3) If there are only 5 suspects, why are there 6 DNA samples?
4) Explain why you added restriction enzymes to each of the DNA samples. In
other words, why did you perform a restriction digest on the samples? Use the
term recognition sequence in your answer.
5) How did you perform a restriction digest on the samples?
6) EcoRI and PstI restriction enzymes come from E. coli bacteria. E. Coli bacteria
live in your intestines. Why do you think you had to incubate the enzymes +
DNA at 37C?
7) What is a restriction digest and what does it have to do with gel electrophoresis?
1) What were the names of the 6 DNA samples?
“Crime Scene” and “Suspect 1” (…2,3,4,5)
2) How many suspects are there in this activity?
Five
3) If there are only 5 suspects, why are there 6 DNA samples?
One sample was collected from the crime scene. Presumably, this sample was
left at the scene by one of the suspects. If the banding pattern produced from
the digested CS sample matches the pattern from one of the suspects, it can
be concluded that that suspect was at the scene of the crime.
4) Explain why you added restriction enzymes to each of the DNA samples. In
other words, why did you perform a restriction digest on the samples? Use the
term recognition sequence in your answer.
Each suspect has a unique sequence of DNA nucleotides. Therefore each
suspect has a unique number and location of recognition sequences for the
EcoRI and PstI restriction enzymes. Therefore, the samples will all have a
unique number and/or size of DNA fragments that result from the digestion.
5) How did you perform a restriction digest on the samples?
Add restriction enzymes to the DNA and incubate at 37C for 45 minutes.
6) EcoRI and PstI come from E. coli bacteria. E. Coli bacteria live in your
intestines. Why do you think you had to incubate the enzymes + DNA at 37C?
Every enzyme has a set of physical conditions (temperature, pH, etc.) at which
it performs best. 37C is human body temperature. These bacteria live in the
human body. The enzymes have evolved to function best at this temperature.
7) What is a restriction digest and what does it have to do with gel
electrophoresis?
A restriction digest is a chemical reaction where restriction enzymes cut up a
strand of DNA into smaller pieces based on the number and location of
recognition sequences the DNA possesses. This results in a homogenous
solution of DNA fragments of various length. Because DNA is super small and
invisible, we must run it through a gel in order to separate the fragments
according to size. This way, we are able to tell differences between one
person’s DNA and another’s.