Question

Read the scenario.

A graduate student is running a PCR reaction to study DNA extracted from an Egyptian mummy. The reaction does not seem to be working, so he checks his notes to see what he added to the reaction mix. He find the following list: mummy DNA, DNA polymerase, and DNA nucleotides.

What is the error in the setup?

A. He forgot to add DNA ligase.
B. He should have added DNA ligase instead of DNA polymerase.
C. He forgot to add primers.
D. He should have recognized that PCR cannot work on DNA extracted from a mummy.

Answer 1

Answer:

C. He forgot to add primers.

Explanation:

The major components of a PCR include:

• A sample DNA which is the DNA that needs to be amplified.
• A DNA polymerase, an enzyme that synthesizes new DNA strands from the sample DNA.
• A primer which represents the starting sequence for the new strand of DNA to be synthesized.
• Free nucleotides in form of Deoxynucleoside triphosphates (dNTPs)

The graduate student forgot to add primers which are essential as a starting point on which the synthesis of new DNA strand is based. DNA ligase is not needed for PCR, but during DNA replication.

The correct option is C.