PCR Study Exam Questions & Answers
2024/2025
Describe the purpose of PCR - ANSWERSPolymerase chain reaction is a technique used to target specific
fragments of DNA and artificially amplify (increase their quantity) them.
Explain the use of primers in PCR - ANSWERSThe primer is an artificial strand of DNA that is made with a
complimentary base sequence to the beginning of the DNA fragment to be amplified. It is used to locate
the specific DNA target sequence to be copied
Describe the process of PCR - ANSWERS1. The DNA fragment to be copied is mixed with a pool of free
DNA nucleotides and heat resistant DNA polymerase enzyme (Taq polymerase which does not denature
at high temperatures)
2. Two primers are made in the laboratory which have matching base pairs to the 3' ends of the DNA
fragment and are added to the mixture
3. The mixture is heated to 93 degrees, then 55 degrees, then back to 72 degrees. This is one complete
cycle
Explain what is involved in the 'thermal cycling' of PCR - ANSWERS- heat to 93 degrees: two DNA strands
seperate
- Add the primers, cool to 55 degrees so that they bind (anneal) to the DNA
- Raise temperature to 72 degrees, DNA polymerase adds DNA nucleotides to seperate strands starting
at primers
- Repeat the process until enough DNA is made
Describe the uses of PCR - ANSWERS1. For DNA fingerprinting, to identify a person by blood or tissue left
at a crime scene
2. To test for genetic diseases in a growing embryo, using embryonic cells
3. Using chloroplast DNA to research plant evolution
2024/2025
Describe the purpose of PCR - ANSWERSPolymerase chain reaction is a technique used to target specific
fragments of DNA and artificially amplify (increase their quantity) them.
Explain the use of primers in PCR - ANSWERSThe primer is an artificial strand of DNA that is made with a
complimentary base sequence to the beginning of the DNA fragment to be amplified. It is used to locate
the specific DNA target sequence to be copied
Describe the process of PCR - ANSWERS1. The DNA fragment to be copied is mixed with a pool of free
DNA nucleotides and heat resistant DNA polymerase enzyme (Taq polymerase which does not denature
at high temperatures)
2. Two primers are made in the laboratory which have matching base pairs to the 3' ends of the DNA
fragment and are added to the mixture
3. The mixture is heated to 93 degrees, then 55 degrees, then back to 72 degrees. This is one complete
cycle
Explain what is involved in the 'thermal cycling' of PCR - ANSWERS- heat to 93 degrees: two DNA strands
seperate
- Add the primers, cool to 55 degrees so that they bind (anneal) to the DNA
- Raise temperature to 72 degrees, DNA polymerase adds DNA nucleotides to seperate strands starting
at primers
- Repeat the process until enough DNA is made
Describe the uses of PCR - ANSWERS1. For DNA fingerprinting, to identify a person by blood or tissue left
at a crime scene
2. To test for genetic diseases in a growing embryo, using embryonic cells
3. Using chloroplast DNA to research plant evolution
