Scientists can perform a process called polymerase chain reaction in the lab to copy DNA inside a test tube. This method is part of creating a DNA fingerprint of a suspected criminal. Cells from the suspect's cheek are placed into a tube. They are popped open, and all the proteins and lipids are removed from the solution. The strands of DNA are separated by heating, and polymerase is added to copy the DNA. What necessary component of DNA replication has been left out of this description?

The correct answer will be - DNA primers

Explanation:

The polymerase chain reaction is a widely used technique which replicates the DNA from a small sample of DNA in in-vitro conditions.

The mechanism of the Polymerase chain reaction is similar to the DNA replication mechanism which requires a DNA polymerase enzyme which in PCR is Taq polymerase and Primers which assists the DNA polymerase to begin the replication.

Since in the given question, the scientist added the DNA polymerase enzyme but forgot to add the single-stranded DNA called primers.

Therefore, primers are the correct answer.