A DNA sequence is amplified by PCR from a small amount of DNA obtained from a crime scene (see figure below left). The PCR product contains two recognition sites for a restriction enzyme called Eco Ri. The positions of the PCR primers are indicated by arrows. The location of the two EcoRI sites and
the beginning and end of the sequence are indicated.
a. Predict the size of the DNA bands you would see on a gel after PCR. No restriction enzyme has been used. How big is the piece of DNA made by
PCR?
b. Predict the size of the DNA bands you would see on a gel after PCR AND digestion with Eco RI. Now the restriction enzyme has been used to cut the
long piece of DNA as shown. How big is each piece?
C. The DNA of three suspects was screened by PCR and digestion with EcoRI. Observe the gel picture on the right below. Which of them would you
identify as being at the crime scene? The long piece of DNA with the two EcoR1 restriction sites is the DNA recovered at the crime scene. Which
subject's fragment pattern matches the crime scene DNA when it is cut with EcoR1?
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